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https://github.com/jeremy-cc/solarch-assoc

Solutions Architech Associate
https://github.com/jeremy-cc/solarch-assoc

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Solutions Architech Associate

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README 

        
# Solutions Architech Associate

##### Exam notes



###### FAQs:



1. [S3](https://aws.amazon.com/s3/faqs/)

2. [Cloudfront](https://aws.amazon.com/cloudfront/details/#faq)

3. [EC2](https://aws.amazon.com/ec2/faqs/)

4. [SQS](https://aws.amazon.com/sqs/faqs/)

5. [EFS](https://aws.amazon.com/efs/faq/)

6. [EBS](https://aws.amazon.com/ebs/faqs/)

6. [ELB Classic](https://aws.amazon.com/elasticloadbalancing/classicloadbalancer/faqs/)

7. [IAM](https://aws.amazon.com/iam/faqs/)

8. [DynamoDB](https://aws.amazon.com/dynamodb/faqs/)

9. [ECS](https://aws.amazon.com/ecs/faqs/)



###### Documentation:



1. [AWS Autoscaling FAQ](http://docs.aws.amazon.com/AutoScaling/latest/DeveloperGuide/AutoScalingBehavior.InstanceTermination.html)

2. [AWS VPC Security Groups](https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_SecurityGroups.html)  

3. [AWS Storage Gateway](http://docs.aws.amazon.com/storagegateway/latest/userguide/storage-gateway-vtl-concepts.html)

4. [AWS IAM identify federation](http://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_providers_enable-console-saml.html)



###### White Papers:

        

1. [AWS Security White Paper](https://d0.awsstatic.com/whitepapers/Security/AWS_Security_Best_Practices.pdf)     

2. [AWS Well Architected Paper](http://d0.awsstatic.com/whitepapers/architecture/AWS_Well-Architected_Framework.pdf)   

3. [AWS Cloud Best Practices](https://d0.awsstatic.com/whitepapers/AWS_Cloud_Best_Practices.pdf)

4. [AWS DR White Paper](http://d36cz9buwru1tt.cloudfront.net/AWS_Disaster_Recovery.pdf)

 

###### Developer Documentation:

 

1. [Common headers for REST requests - S3](http://docs.aws.amazon.com/AmazonS3/latest/API/RESTCommonRequestHeaders.html)

 

------



##### General notes on AWS



###### Regions and AZs:



1. A region is a distinct geographical area that comprises multiple Availability Zones

2. An availability zone is an isolated data centre or cluster of data centres that hosts AWS services within a region.

   A region contains at least two availability zones.

3. an Edge logation is an access point for AWS services - this is generally hosted in major urban areas, and is used

   mainly by systems such as CloudFront

   

   

###### IAM

   

1.  IAM is a global service, not bound to a region.  

2.  IAM comprises users, groups, roles and policies.  

3.  Users can have api access (access keys) or username + password access ( console login ) - a user cannot log in

    to the console with an access key

4.  A policy is a document that describes a collection of permissions.

5.  A group is a logical collection of users. A user can belong to multiple groups, but a group cannot belong to other groups.

6.  Groups can be granted permissions via policies

7.  A role is a collection of permissions or policies, e.g S3AdminAccess, and you can have a soft max of 500 per account.

8.  The term 'Owner' refers to the email address and account id of the account in which IAM policies, roles etc are created.

    

###### IAM Roles

1.  Role types:

    1. AWS Service roles - permit AWS services to call other services on your behalf

    2. AWS Service linked roles - used for bots for things like Alexa / Polly

    3. Roles for cross account - permit one account to call another account, either yours or 3rd party

    4. Roles for Identity Provider access - permit OpenID, Single sign on etc access to AWS account

    

###### S3 - Simple Storage Service

    

1.  S3 is a global namespace.  Bucket names must be unique across S3, not just across your account or region.

2.  URL Format:  https://s3-[region].amazonaws.com/[bucketname] or http://[bucketname].s3-[region].amazonaws.com, 

s3://[bucketname] in the cli

3.  Website hosting format: http://[bucketname].s3-website-[region].amazonaws.com or http://[bucket-name].s3-website.[region].amazonaws.com



4.  S3's consistency model is:

    1. Read after write consistency for PUT (new objects) 

    2. Eventual consistency for Overwrite or delete (has non-zero propagation time)

5.  S3 sorts lexographically - data will stored in the same physical area on S3 and can cause performance bottlenecks.

    Consider salting file names with a random prefix for distribution

6.  Subresources

    1. ACL - fine-grained permissions - at bucket level or at object level

    2. Torrent - supports BitTorrent protocol

7.  SLA availability 99.9% but built for 99.99% - 11 9's durability guarantee

8.  Flavours

    1. S3 - IA (Infrequently accessed) - much cheaper

    2. S3 - RR (Reduced redundancy) - 99.99% availability over a year

    3. S3 vs Glacier - Glacier much cheaper but takes 3 - 5 hours to access data

9.  Charged for storage, request counts, storage management, data transfer, transfer acceleration

10.  For Cross Region Replication, versioning must be on in the source and target buckets.  CRR will only replicate NEW objects.

    Old objects will be replicated if they are updated, and their entire history will be replicated as well.

    Object deletes are replicated but Object VERSION deletes are NOT replicated.

11. S3 can be secured either via bucket policy or via ACLs

12. Transfer acceleration - use Cloudfront Edge location to speed upload to backing S3 bucket.

    

###### CloudFront



1.  Edge location - point at which content will be cached 'locally'

2.  Origin - original source of data (EC2, ALB, S3, Route53)

3.  Distribution - CDN consisting of 2 to N Edge locations

4.  You can read from and write to Edge locations - writes are cached for the object's TTL.  You can expire early but you

    will be charged.

5.  Two types - Web & RTMP     

6.  TTLs must be set to match periodicity of content

7.  Use signed cookies or urls to enforce access control onto resources.

8.  15-20 mins to provision a distribution.

9.  Possile to customise HTTP responses; restrict or permit (white XOR blacklist) by geographical location;  

10. Can create an *invalidation* to prevent caching of specific media objects on edge locations - billable.

11. PCI/DSS and HIPAA compliant



###### Encryption

    

1.  In transit

    SSL/TLS

2.  At rest

    1. Server-side

        1. S3 managed keys - AES256 : SSE-S3

        2. SSE with KMS managed keys : SSE-KMS - permissioned envelope key + audit trail

        3. SSE with customer-provided keys - customer manages keys - SSE-C

    2. Client-side

        1. Encrypt client side, upload encrypted data to S3



###### Storage Gateway



1. acts as a async gateway between on-premise systems and AWS storage infrastructure (S3 and potentially Gateway)

2. downloadable as a virtual machine image - install and associate with AWS account

3. GW types:

   1. File Gateway (NFS) - store flat files in S3.  Permissions, ownership etc are stored as S3 metadata.  Once they are

   in S3 they can be managed as usual in S3 - versioning, ACL, bucket policies etc.

   2. Volumes Gateway (iSCSI) - store block 

      1. Stored volumes - store entire volume on premise.  Snapshots are written to AWS - use case for e.g backups.

      2. Cached volumes - store frequently accessed items locally, but S3 is the main data store for infrequent access.

      

      Volumes Gatway devices are virtual hard drives which can be saved as EBS snapshots (deltas) on AWS.

   3. Tape Gateway - VTL, create tape images then sync to AWS

      

###### Snowball

1. Legacy app was Import/Export - clients shipped physical drives to AWS for import but managing this became uneconomical

and impractical at large scale

2. 3 Types

   1. Snowball - beer-crate sized storage device.  Tamper-resistant, encrypted at rest, erased by Amazon once migration is complete

   2. Snowball Edge - similar sized appliance but has compute capabilities as well as just storage.  Essentially a small mobile

      AWS Data center that can cluster.  Support Lambda functions. 

   3. Snowmobile - peta/exabyte scale mobile AWS datacenter on truck.     

             

        

------



##### AWS Compute

        

###### EC2 - Elastic Compute Cloud

        

1.  There are four instance types

	1. On Demand

	2. Reserved (typically cheaper than on demand) - can be moved between AZ's

	3. Spot (available at spot market rate, can be terminated at any point)

	4. Dedicated Host (can be paid for by the hour)

2.  Spot instances - if the instance is terminated by AWS you do not pay for a partial hour of usage; if you terminate it you will be charged for any hour the instance ran

3.  Instance families



        |  family        | Optimised for         |

        |  C             | Computation           |

        |  D             | Storage - Warehousing |

        |  F             | FPGA                  |

        |  G             | Graphics Intens       |

        |  I             | I/O  - RDBMS,NOSQL    |

        |  M             | General Purpose       |

        |  P             | Graphics / GPU        |

        |  R             | Memory (app/db)       |

        |  X             | Memory (Spark/bigdata)|

        

4. AMIs can be EBS backed or Instance Store (Ephemeral Storage) backed.

   1. Instance Store-backed instances

   	  1. You cannot attach additional IS volumes once an IS instance is running

   	  2. You can only reboot or terminate an IS-backed instance.  Rebooting will not result in data loss; terminating will.

   	  3. If the hypervisor under a IS-instance fails, you will lose your data. 

   	  4. IS volumes do not display in the console.

   	  5. IS volumes are only available on some EC2 families - many are EBS only

   	  6. IS root volumes are created from S3 templates

   	  7. IS volumes are deleted on instance termination - no option to preserve the data.

   2. EBS-backed instances

      1. EBS (Elastic Block Store) is a newer backing tech than Instance Store

      2. EBS root volumes are created from EBS snapshots - typically faster than IS volume creation.

      3. Root volumes are deleted on termination by default but you can instruct AWS not to delete EBS. 



5. instance metadata is available at http://169.254.169.254/latest/meta-data      

   

###### EC2 Placement Groups

   

1.  A Placement Group permits a set of EC2 instances to be grouped logically within an AZ; 

2.  Instances within a placement group share a low latency 10Gbps network

2.  A Placement Group is specific to an AZ - it cannot span AZs

3.  A Placement Group must be uniquely named within the Account

4.  Limited to optimised instances (Compute / GPU / Storage / Memory optimised)

5.  AWS recommend homogenous instances within a placement group

6.  You cannot merge placement groups

7.  You cannot move running instances into a placement group; all instances must be launched into the placement group



###### EFS (Elastic File System)



1.  Works via NFS v4, mounted as a standard fs by domain name.  Available for any Linux instance.

2.  Pay for usage, not preprovisioned size.

3.  Scales to PB, supports thousands of concurrent NFS connections

4.  Data is stored across AZ's and EFS is available concurrently to all instances in a VPC, independent of AZ.

5.  Block-based storage as opposed to object based (e.g S3)

6.  Read-after-write consistency.

7.  Good solution for sharing a usable filesystem between instances - e.g. code for websites / applications?

8.  EFS offers high throughput for worse overall latency re EBS.

9.  General purpose mode vs Max I/O for an EFS that is massively concurrent

10. EFS can be mounted across a Direct Connect link.  EFS is not available over VPN.

   

###### EBS (Elastic Block Storage)

        

1. Create logical block devices and attach them to EC2 instances.  Great for keeping filesystem deltas where if

   an instance dies you need to keep the data (e.g. jenkins CI)

2. EBS are in an AZ and are automatically replicated.

3. Types:   

   1.  SSD (GP2) - 3 IOPS (io/s) per gigabyte.  Up to 10k iops and burst of 3k iops/s for volumes < 1 Gb, bootable

   2.  Provisioned IOPS (IO1) - use for > 10k iops, bootable

   3.  Throughput-optimised HDD (ST1) (Magnetic) - Big Data / Warehousing / Log processing.  Sequential data, cannot be boot volumes

   4.  Cold HDD (SC1) -  fileservers.  low cost / infrequently accessed - cannot be boot volumes

   5.  Magnetic (Standard) - lowest cost / gig , bootable

4. EBS can only bind to one instance at a time.  For multiple instance sharing you have to use EFS

5. Never, ever create a Raid 5 device on EBS.  Amazon strongly de-incentivises this.

6. Snapshots of encrypted volumes are encrypted.  Likewise volumes restored from encrypted snapshots are encrypted.

7. You can only share unencrypted snapshots since the encryption keys are bound to your AWS accounts.  

8. You cannot delete an EBS snapshot if it is used as the root volume of a registered AMI.

9. EBS offers lower overall throughput but decreased latency as opposed to EFS.

   

###### Security Groups

   

1. Changes take place immediately

2. New security groups permit all egress traffic by default

3. Security group ingress rules are automatically mirrored to egress - unlike VPC. 

4. All inbound traffic is blocked by default; you can only PERMIT traffic.  You cannot DENY specific traffic.

5. 1 SG can apply to an infinity of EC2 instances

6. An instance can have 5 SGs bound to it



###### Load Balancing And Health Checks



1. ALBs work at the application layer, support path based routing, and are recommended for HTTP traffic. Classic load

   balancers work at application or transport level but cannot do path-based routing.

2. ALBS route via Target Groups; Classic LBs route directly to EC2 instances.   

3. EC2 instances monitored by an ELB are reported as InService or OutOfService.

4. Health checks are conducted by connecting to the instances within an ALB or CLB.

5. ELBs are always addressed by DNS name; no IPv4 address is published for them.

6. It's advisable to have an ALB in two or more subnets across different AZ's to provide redundancy in case an AZ

goes offline.  This is especially true for public ALBs - you should have two different public subnets in different AZs



###### ASG and Autoscaling



1. Default termination policy -

   1. Find AZ with most instances and at least one unprotected instance.  

   2. If AZs have similar instance counts, terminate the instance with the oldest launch configuration.  

   3. If multiple instances use same launch configuration, find instance closest to next billing hour, and multiple match this kill one at random.

2. Custom termination policies are:

   1. Oldest Instance first

   2. Newest instance first

   3. Oldest Launch Configuration

   4. Closest To next instance hour

   5. Default



###### Cloudwatch



1. Free tier updates metrics every 5 minutes; Detailed monitoring has granularity of 1 minute but is not free.

2. Metrics are for any Cloudwatch-enabled service

3. Default metrics for an EC2 instance are always CPU,Disk,Network and Status related by default.

4. Cloudwatch Alarms - permit notification when metrics exceed preconfigured limits e.g. 80% cpu usage, min credit etc. 

5. Cloudwatch Events - permit async rule-based triggers in response to Cloudwatch events e.g calling a Lambda function.

6. Cloudwatch Logs - permit log analysis such as exception monitoring, httpd access logs, Lambda execution logs etc.

 

###### Lambda



1. Serverless compute service that abstracts away all lower level systems and abstractions.

2. Can be triggered from events (e.g. Cloudwatch) or in response to HTTP requests (API Gateway)

3. Need CORS permission - Access-Control-Allow-Origin: * 

4. Can be run in the default VPC or bound to a specific VPC

5. Can be allocated security groups within a VPC

6. Good way to chain events without needing a physical instance.

  

###### RDS

  

1. RDS: Two different types of backup strategies - automated backups and database snapshots

    1. Automated Backups

        1. Automated backups permit recovery to any day within the retention period (1-35 days, defaulting to 7 days)

        2. Automated backups store take a full daily snapshot + transaction logs for the day.

        3. When restoring, the most recent Automated Backup is chosen and restored, followed with TX logs for the day,

       permitting recovery up to the second.

        4. Automated backups are enabled by default, and are backed up to S3.  Free S3 storage equivalent to RDS instance size

        5. Backups are taken during a defined window; during which time I/O latency may increase and storage I/O may be suspended

        6. Automated Backups are deleted if you delete the source RDS instance

    2. DB Snapshots

        1. DB snapshots are manual

2. Restored Automated backups AND snapshots are always created as a NEW RDS INSTANCE with a new endpoint - you cannot restore over

   an existing database instance.

3. Encryption at reset is supported, but you cannot encrypt an existing database; you need to create a new encrypted

   instance and migrate your unencrypted data into the encrypted instance.  Once an RDS instance is encrypted, all

   automated backups, snapshots and read replicas are encrypted as well.

4. Multi-AZ - you can have an RDS as a syncronous replica of an existing RDS in a separate AZ; if your primary RDS 

   fails, but you are set up Multi AZ, AWS will automatically fail over to the backup RDS using the same domain name.

   This is a DR solution, not a SCALING solution.

5. Read replicas are async replicas of the primary DB which can be used to boost performance.  This is a SCALING solution

   not a DR Solution.

   1.  Require automatic backups to be enabled

   2.  Can have up to 5 read replicas on a RDS instance

   3.  Can have read replicas of read replicas but latency stacks up very quickly. 

   4.  Each read replica has its own DNS entry.  Read replicas cannot be chained in Multi-AZ.  You can create read

   replicas of a Multi-AZ source DB though.

   5.  Read replicas can be promoted to source databases, but this breaks replication.

6. RDS scaling requires manual intervention e.g stopping instance to resize it.   

   

###### DynamoDB

                           

1. Is a fast NoSQL DB service backed by SSD drives

2. Supports documents AND key/value pairs.  Good fit for Web / Mobile / Game / IoT

3. Stored on SSD, spread across 3 geographically distinct facilities (not necessarily AZ's)  

4. Supports Eventually Consistent Reads (1s consistency), Strongly-consistent reads (returns all data which was successfully written prior to read)                           

5. Pricing by provisioned throughput capacity

    1. Write throughput, hourly fee per 10 units

    2. Read throughput, hourly fee per 50 units

    3. Storage costs

6.  Expensive for writes, cheap for reads.

7.  Push-button scaling; can scale reads + writes on the fly    

8.  Reads can be flagged as eventually consistent (higher throughput) or strongly consistent.

9.  400k limit on record size

10. Can scale up and down without an outage.

11. No upper limit on storage size or throughput

12. Global Secondary Indexes do not require unique keys and are eventually consistent.  GSI's function almost like a meta-table.

13. If a GSI exhausts its throughput then writes to the table or tables underlying the GSI could be throttled.

    

###### Red Shift

 

1. Modes

    1. Single Node

    2. Multi-node which comprised a Leader node (manages clients) and up to 128 compute nodes (manage calculations)

    3. Column-based - used for aggregate queries and statistics

2. Distributes queries and data across all available nodes

3. Pricing

    1. compute node usage - 1 unit per node per hour

    2. backup

    3. data transfer, within a vpc

4. Encryption in transit, encrypted at rest using AES-256, can manage keys through hardware or KMS

5. Single AZ

6. Can restore snapshots to a new AZ if there's an outage.

7. Can be used to reduce load on primary transactional dbs caused by management running OLAP reports etc.



###### Elasticache



1. Permits deployment, operation and scale in-memory caches in AWS

2. Engines

    1. Memcached

    2. Redis - supports Multi-AZ and Master/Slave replication

3. Elasticache is a good choice to help reduce latency between app and db by caching results of calcs if the database

    is read heavy

    

###### Aurora

    

1. Maintains 2 copies of DB per AZ, minimum of 3 AZs, minimum of 6 copies of data.

2. Designed to sustain loss of 2 copies without affecting write availability and 3 copies without affecting read

    availability

3. Storage is self-healing

4. Two types of replicas

   1. Aurora replicas (up to 15) - fail over automatically

   2. Mysql Read Replicas (up to 5) - will require intervention to fail over

5. Supports ORACLE, MySQL, SQL, Postgres     

 

------

##### AWS Networking

###### Route 53



1. Route53 is a GLOBAL service

2. SOA record holds

    1. server that supplied zone data

    2. administrator contact details

3. An  A Record translates a domain name to an ip address.  This means you cannot route to a ELB via Route53 A record as ELBs do not have

    ipv4 or ipv6 addresses, just an amazon DNS entry.  

3. an Alias(AWS specific) record can be used to map to

    1. an ELB's public dns hostname

    2. a Cloudfront distribution

    3. an S3 bucket that has been configured as a public website

    4. an Elastic beanstalk environment.   

    Basically an Alias maps Route53 to other AWS web-enabled services.  

    

    AWS Alias records are specific to AWS and are not a DNS standard.  ALIAS records can map to zone apexes, and map these

    most commonly to ELBs. ALIAS records update transparently when for e.g. a backing ELB changes internal dns name; this

    change is completely opaque to the outside world.

5. TTL - cache length of DNS entry on server or resolving client.  No defaults per service

6. CNAME - can resolve one domain name to another.  CNAME cannot map to the zone apex e.g google.com.  CNAME could map

   www.google.com

7. Routing policies for AWS Alias records:

    1. Simple (default) - most commonly used for single resource (e.g. single webserver)

    2. Weighted

        1. permit routing of traffic by weight e.g 80% to one region and 20% to another region.  Could also be used for A/B

       testing for e.g.

        2. weighting is ON AVERAGE - on average over time x % will go to A and y % will go to B.  Max weight for route is 255, min 0.

    3. Latency

        1. Route based on lowest network atency for end user - create a latency resource record set in every region 

        that hosts your site.  R53 selects latency resource set with lowest latency.

    4. Failover

        1. Routing policy for active/passive failover

        2. R53 monitors health of primary site via a health check; if health check fails then R53 routes to the failover site.

        3. R53 Health check url cannot be the url of the ALIAS record; it must be the url of the ELB endpoint

    5. Geolocation

        1. permits traffic routing based on geographical location

        2. Geolocation can be done by Continent (e.g. Europe), by Country (e.g Germany) or by State in the case of the USA.

8. Route 53 is a fully fledged DNS system e.g it supports MX records        

9. Route 53 is billed on usage only.

    

###### VPC



1. VPC acts like a logical datacenter in a region - cannot span regions

2. Consist of Internet Gateway or VPG, Route Tables, ACLS, Subnets and SG's

3. VPC Creation

    1. Cannot create a CIDR block greater than /16 for a VPC

    2. When a VPC is created, a MAIN route table is created with it.

    3. When a VPC is created, a default security group is created for the VPC

    4. When a VPC is created, a default Network ACL is created for the VPC

4. Subnets are bound to a single AZ within a region. ACLs and Security Groups can span AZs.  Subnets are associated

   to the MAIN route table by default on creation.

5. 3 addresses are reserved by default in a subnet, not including .0 and .255 

   a.b.c.1 is reserved for the VPC router.  a.b.c.2 is reserved for DNS and a.b.c.3 is reserved for future use.

   .255 is broadcast, but broadcast isn't possible in VPC so this is simply reserved.

6. To connect a VPC to the internet you need to create an Internet Gateway.  Only one IG can be bound to a VPC.

7. VPC can peer to other VPCs in different accounts.  NO transitive VPC peering though. VPCs must peer directly with one another

8. A VPC that has been set to Dedicated hosting mode cannot be reset to Default hosting mode.  Only submodes of dedicated can be selected.

9. VPCs that peer to one another can only route vpc traffic to one another, not edge traffic.



###### NAT Instances and NAT Gateways



1. NAT-G released in 2016.  Old method was NAT instances.  NAT Gateways scale automatically, no need to patch or put in SG's - AWS manage everything.

2. NAT instances are provisioned from specific NAT Amis

3. EC2 instances have a default Source/Dest check which checks that traffic to them is either for or from them.  A NAT instance

needs to be able to route traffic so this setting needs to be disabled.

4. NAT Instances are configured as the targets of routing tables in much the same way as IG's are. 

5. NAT instances must be in a public subnet and must have an elastic IP allocated to them.

6. NAT instance traffic max throughput depends on instance size

7. NAT instances require scripts to do failover in HA

8. Private subnets must have a route to the NAT instance in order to see the public internet through them.

9. NAT Gateway is always deployed into subnets which are or can face PUBLIC internet - it is automatically given a public ip address

10 . NAT Gateway doesn't require a SG or disable of source/dest traffic check

                                     

###### Network Access Control Lists



1. Operates at the subnet level; unlike SGs ACLS support both allow and deny rules.   SGs can only PERMIT, everything is denied by default.

2. Unlike SGs, ACLs are stateless.  Both incoming and outgoing traffic has to be explicitly allowed; it is not implicitly

   allowed like SGs.

3. Rules are processed in numerical order to decide whether to permit or deny traffic.   

4. Automatically enacted on all instances in a subnet that has an ACL defined, unlike SGs which need to be explicitly added

    to instances

5. A VCP comes with a default ACL which allows all inbound and outbound traffic by default.  Subnets are associated with this

default ACL unless they are assigned to a custom ACL.  Subnets must always be a member of one and only one ACL. 

6. A custom ACL denies all inbound and outbound traffic by default when created.

7. An ACL can apply to multiple subnets in multiple AZs but a subnet can only be associated with a single ACL

8. Amazon recommend rule numbers incrementing in hundreds e.g 100,200 etc - this gives space to make later amendments.        

9. Ephemeral ports - you need to open ephemeral ports (1024-65535) if you for e.g have a webserver on an instance.

10. Remember that rules are evaluated in order.  If you're going to block specific ip addresses or ports you need to do this

   BEFORE you have any global permissive rules for e.g

   

###### Bastions vs NATs

   

1. NAT routes internet traffic from public subnet to private subnets

2. BASTION host permits ssh connections from public internet, and from there can act as a staging host to jump to internal servers



###### Resilient architecture

1. Always have at least two subnets in two different AZs

2. Use autoscale groups with a min size of 2

3. Use Route53 with round robin or health-check routing to fail over

4. NAT instances are tricky to HA - you need one in each public subnet, with different ips, and scripts to fail over between them.

NAT Gateway is a better solution.



###### VPC Flow Logs   

  

1. Permit you to capture traffic logs a la wiresark, tcpdump

2. Can then push data to CloudWatch for metrics and analysis



------

##### AWS Application Services

###### SQS



1. Oldest AWS service

2. Visibility Timeout window - message processed by one client is invisible to other clients till timeout expires.

3. 256kb payload size

4. Queue acts as a buffer

5. Autoscaling groups can be configured to provision based on SQS queue size

6. Standard Queues and FIFO Queues - FIFO are new.

    6.1 Standard (Default) queues - unlimited Tx/s, messages guaranteed at least once, more than one copy might be delivered out of order - no guarantees of ordering.

    6.2 FIFO - guaranteed delivery order.  Remains available until consumer deletes message. Limited to 300 Tx/s

7. SQS is pull based, not push based.  256k max payload, Message TTL from 1 minute to 14 days, defaults 4 days

8. Max Visibility Time Out is 12 hours     

9. SQS Long Polling - attempt to get message; block and wait for message

10. SQS maintains no application state; app needs to track this

11. 'DelaySeconds' blocks message visibility from all consumers for the period when the message is published

    

###### SWF - Simple Workflow Service



1. Workers are applications that interact with SWF to get tasks, process tasks and return results

2. Starter is the application that initiates an SWS process e.g your website.  

   Decider is the orcestrator : controls scheduling, concurrency and ordering based on app logic.

   Activity works perform the work associated with each task.

3. SWF guarantees tasks assigned once, never duplicated 

4. SWF maintains app state so workers and deciders don't need to and can scale quickly as a result

5. Domains isolate units for a work flow / process into logical groups

6. Max Workflow TTL is a year, expressed in seconds

7. SWF presents a task-orientated API whereas SQS presents a message-orientated API



###### SNS

    

1. Can deliver push notifications to many cloud systems; also SMS, SQS or HTTP endpoints

2. Messages are stored redundantly across multiple AZs

3. Can spool to multiple recipients via topics.  Topics can also spool to multiple different endpoint types.

4. Instantaneous, push-based delivery.  Simple APIS, flexible message delivery. 

5. Pay as you go cost

6. SQS is poll, SNS is push



###### API Gateway



1. API-G is a facade that can provide serverless computing through lambda etc

2. API-G supports caching and throttling

3. API-G scales automatically with load

4. API-G can log to CloudWatch



###### Kinesis



1. Kinesis is a sink for Streaming Data - permits analysis and creation of custom apps based on the data.  

2. Kinesis core services

    1. Kinesis Streams

        1. Data stored for 24h (default) -> 7 days(max). Data is sharded.  

        2. Consumers (Ec2 instances) run transformations against the Stream data

        3. Consumers forward calculations on for persistance elsewhere

        4. Data capacity of Kinesis stream is sum(capacity of shards in stream)

    2. Kinesis Firehose

        1. Automated aggregation and processing of data - persists direct to SE, analysis etc is optional.

        2. Firehose has no data persistence itself.

        3. Data is either analysed vi Lambda, or else persisted straight to S3.

        4. Firehose can write Kinesis data into Elastic Search

    3. Kinesis Analytics

        1. Permits you to run SQL queries on data within Firehose or Streams; queried data can be stored to S3, RedShift or ElasticSearch

3. Shards implies Streams as Firehose has no shards.  Automatic Analysis via Lambda implies FireHose

        

------



##### White paper overviews

###### Security Process



1. AWS is responsible for securing the underlying infrastructure - you are responsible for anything you put on top of AWS infrastructure. AWS responsible for

security OF the cloud, Customer responsible for security IN the cloud.

2. AWS is responsible for securing services which are classed as managed services, e.g NAT Gateway.  However, customer is responsible for 

securing Users and Roles for these services.

3. EC2, VPC, S3 are all completely under customer control

4. MFA recommended, CloudTrail recommended, SSL/TLS recommended

5. Amazon Corporate network is segregated from AWS Production network.

6. AWS mitigate against DDos, MITM, Packet sniffing, Port scanning, IP Spoofing

7. Different instances on same physical hardware are isolated by Xen hypervisor. AWS Firewall resides in hypervisor layer.  Packets must traverse hypervisor so

all instances on a single physical machine are isolated and have no more access than any other instance

8. Instances run a guest operating system fully managed by customer - AWS have no access to the OS.  EC2 instances run a mandatory internal firewall with a default policy to DENY.

9. AWS provides support for encrypted volumes on more powerful instance types.  AES-256, done on the physical hardware so data is encrypted between EC2 instances and EBS.

10. ELB permits SSL termination on the Load Balancer



###### Well Architected Framework



1. Pillar 1 - Security

    1. Data protection (EBS, S3, RDS encryption in place)

        1. Data should be classified before migration - public, sensitive, classified etc.

        2. Encrypt wherever possible, whether at rest or in transit

        3. Use storage systems that provide versioning, logging, and redundancy to prevent data loss.

        4. AWS never initiates cross-region data migration; this is always initiated by a customer.

    2. Privilege Management (IAM, MFA)

        1. Ensures only authenticated and authorised users can access content. 

            1. ACLS, Passwords, Roles

        2. How is root account secured and accessed

        3. Are roles and responsibilities of system users defined for minimum required access?

        4. How are you limiting automated system access?

    3. Infrastructure security (VPC, SG, ACL)

        1. How are you enforcing network and boundary security.

        2. How are you enforcing AWS service level security?

    4. Detective controls

        1. CloudTrail

        2. CloudWatch

        3. Config

        4. S3 and Glacier

        5. How are you capturing and analyzing logs

2. Pillar 2 - Reliability

    1. Test recovery procedures

    2. Automatically recover from failures

    3. Scale horizontally to increase redundancy

    4. Stop guessing capacity.

3. Pillar 3 - Performance Efficiency

    1. Democratise technology choices - consume tech as a service

    2. Go Global in minutes

    3. Use serverless architecture

    4. Experiment more often

    5. Areas:

        1. Compute

        2. Storage

        3. Databases

        4. Space/Time tradeoff

4. Cost Optimisation

   1. Transparently attribute expenditure

   2. Use managed services to reduce TCO

   3. Trade capital expense for operating expense

   4. Benefit from economies of scale

   5. Stop spending money on Data Centre operations

   6. Trusted Advisor

5. Operational Excellence

   1. Perform changes with code

   2. Small, incremental changes

   3. Test responses to unexpected events

   4. Learn from operational events

   5. Keep procedures current

        

    



------



###### Study points



1. instance sizes and Specific soft + hard limits in a region / AZ

2. Platform PCI certification level - PCI DSS Level 1

3. An existing EBS snapshot can be modified via the CLI, APIs or Console

4. Reserved instances for EC2 and RDS

5. Region count

6. Support level response times based on level

7. US STANDARD is a redundant term.

8. It is possible to transfer reserved instances between AZs in a region.

9. When a question mentions a stateless web tier, that implies no stateful services on the WEB tier i.e. ec2.  

10. CloudFormation - overview and usage



##### Tips



###### Big Data



1. To consumer Big Data - use Kinesis.  To do Business Intelligence on Big Data, use RedShift.  To do Processing, Elastic Map Reduce

2. Redshift column size - 1024k



###### EC2 - EBS vs Instance Store



1. EBS is persistent, Instance Store is ephemeral

2. EBS volumes can be detached and attached to other EC2 instances, Instance Store exists for the lifetime of the instance only.

3. EBS volumes can be stopped.  Instance store volumes cannot be stopped

4. EBS - long term block/based storage; Instance Store should not be used for any storage.



###### OpsWorks



1. Orchestration service using Chef - uses recipes to maintain infrastructure.

2. keywords - chef, recipes, cook books



###### Elastic Transcoder



1. Cloud-based media conversion

2. Pay based on content length and quality of transcoding

 

###### SWF Actors 



1. Workflow starter - application that initiates a SWF workflow

2. Activity workers - applications that interact with a SWF workflow

3. Decider - application that orchestrates a SWF workflow



###### EC2 Meta Data



1. curl http://169.254.169.254/latest/meta-data/



###### GOTCHAS



1. No transfer cost between S3 and EC2 in the same region

2. Instance store backed EC2 cannot be restarted without losing data

3. S3 - RRS provides 99.99% availability, S3 - IA provides 99.9% availability

4. Memory utilisation is a Custom cloudwatch metric, not a default metric

5. You are charged for EIPs which are unallocated or are allocated to a stopped instance - created but not used basically

6. T2 are EBS-only

7. S3 static website bucket name must match the route53 domain name

8. "Run Command" can be used to configure multiple EC2s without requiring a login.

9. Consolidated billing has a paying account and linked accounts

10. "Pilot Light" -> minimal, always-on DR environment.

11. S3 billing is on request count and storage.

12. Glacier archives can be 40Tb in size and are immutable once created

13. A Kinesis consumer reads data from Kinesis streams

14. Kinesis data can persist for a max of 7 days

15.