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https://github.com/juntossomosmais/backend-challenge

🚀 Our hiring challenge to Back-end Developers
https://github.com/juntossomosmais/backend-challenge

apps back-end code-challenge csharp full-stack java javascript kotlin nodejs python

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🚀 Our hiring challenge to Back-end Developers

Awesome Lists containing this project

README 

          


  Juntos Somos Mais




# <backend-challenge />



*[Leia em Português](./README.pt-BR.md)*



The main objective of this challenge is to assess your approach to **problem-solving, code quality, and how you leverage modern tools** — including AI.



We evaluate:



- Your coding style and organization

- Decision-making and trade-offs

- Testing strategies

- Documentation quality

- How you use AI as a development tool



> 🤖 **AI is welcome here.** We don't want to know *if* you used AI. We want to know *how* you used it.



---



## Table of Contents



- [The Challenge](#the-challenge)

- [Business Rules](#business-rules)

- [API Requirements](#api-requirements)

- [Evaluation Criteria](#evaluation-criteria)

- [AI Journey (Required)](#ai-journey-required)

- [Submission](#submission)

- [FAQ](#faq)



---



## The Challenge



We receive customer data from partner companies in both **CSV** and **JSON** formats. Your task is to:



1. **Load** data from external URLs at application startup

2. **Transform** the data applying our business rules

3. **Expose** a REST API to query the processed data



### Input Data



| Format | URL | Records |

|--------|-----|---------|

| CSV | [input-backend.csv](https://storage.googleapis.com/juntossomosmais-code-challenge/input-backend.csv) | ~1000 |

| JSON | [input-backend.json](https://storage.googleapis.com/juntossomosmais-code-challenge/input-backend.json) | ~1000 |



> ⚠️ Data must be loaded via HTTP request **at startup** and kept **in memory**. No database required.



---



## Business Rules



### 1. Customer Classification by Location



Based on coordinates, classify each customer:



| Type | Bounding Box |

|------|--------------|

| **SPECIAL** | minlon: -2.196998, minlat: -46.361899, maxlon: -15.411580, maxlat: -34.276938 |

| **SPECIAL** | minlon: -19.766959, minlat: -52.997614, maxlon: -23.966413, maxlat: -44.428305 |

| **NORMAL** | minlon: -26.155681, minlat: -54.777426, maxlon: -34.016466, maxlat: -46.603598 |

| **LABORIOUS** | Anyone not matching the above |



### 2. Data Transformations



| Field | Transformation |

|-------|----------------|

| `phone`, `cell` | Convert to [E.164](https://en.wikipedia.org/wiki/E.164) format. Example: `(86) 8370-9831` → `+558683709831` |

| `gender` | `male` → `M`, `female` → `F` |

| `dob.age`, `registered.age` | Remove these fields |

| `nationality` | Add field with value `BR` |

| `region` | Add based on state (Norte, Nordeste, Centro-Oeste, Sudeste, Sul) |



### 3. Output Contract



```json

{

  "type": "laborious",

  "gender": "M",

  "name": {

    "title": "mr",

    "first": "quirilo",

    "last": "nascimento"

  },

  "location": {

    "region": "sul",

    "street": "680 rua treze",

    "city": "varginha",

    "state": "paraná",

    "postcode": 37260,

    "coordinates": {

      "latitude": "-46.9519",

      "longitude": "-57.4496"

    },

    "timezone": {

      "offset": "+8:00",

      "description": "Beijing, Perth, Singapore, Hong Kong"

    }

  },

  "email": "quirilo.nascimento@example.com",

  "birthday": "1979-01-22T03:35:31Z",

  "registered": "2005-07-01T13:52:48Z",

  "telephoneNumbers": ["+556629637520"],

  "mobileNumbers": ["+553270684089"],

  "picture": {

    "large": "https://randomuser.me/api/portraits/men/83.jpg",

    "medium": "https://randomuser.me/api/portraits/med/men/83.jpg",

    "thumbnail": "https://randomuser.me/api/portraits/thumb/men/83.jpg"

  },

  "nationality": "BR"

}

```



---



## API Requirements



### Endpoint



```

GET /users

```



### Query Parameters



| Parameter | Type | Description |

|-----------|------|-------------|

| `region` | string | Filter by region (norte, nordeste, centro-oeste, sudeste, sul) |

| `type` | string | Filter by classification (special, normal, laborious) |

| `pageNumber` | int | Page number (1-indexed) |

| `pageSize` | int | Items per page |



### Response



```json

{

  "pageNumber": 1,

  "pageSize": 10,

  "totalCount": 2000,

  "users": [...]

}

```



### Validation



Your API must pass our validation script:



```bash

./validate.sh

```



This checks:

- Endpoint responding at `localhost:8080`

- Pagination fields present

- Total count of 2000 records



---



## Evaluation Criteria



We assess your submission across **7 competencies**. There are no "levels" to choose — just deliver your best work, and we'll evaluate where you stand.



### 1. 🎯 Problem Solving



| What we look for |

|------------------|

| Correct implementation of all business rules |

| Edge cases handling (invalid data, missing fields, malformed input) |

| Logical and efficient approach to data transformation |



### 2. 🏗️ Code Architecture



| What we look for |

|------------------|

| Clear separation of concerns |

| Consistent project structure |

| Appropriate use of design patterns (when they add value, not for show) |

| Code that's easy to navigate and understand |



### 3. ✨ Code Quality



| What we look for |

|------------------|

| Readability over cleverness |

| Meaningful naming conventions |

| Consistent style throughout |

| No unnecessary complexity |

| Proper error handling |



### 4. 🧪 Testing



| What we look for |

|------------------|

| Tests that document behavior |

| Coverage of critical paths |

| Tests that would catch real bugs |

| Balance between unit and integration tests |



### 5. 📚 Documentation



| What we look for |

|------------------|

| Clear README with setup instructions |

| API documentation (any format) |

| Comments where code isn't self-explanatory |

| Architecture decisions explained (when relevant) |



### 6. 🚀 Production Readiness



| What we look for |

|------------------|

| Containerization (Docker) |

| Environment configuration |

| Health checks |

| Logging strategy |

| CI/CD awareness |



### 7. 🤖 AI Collaboration



| What we look for |

|------------------|

| Transparency in AI usage |

| Critical thinking about AI-generated code |

| Iteration and refinement over copy-paste |

| Understanding of what the AI produced |



---



## AI Journey (Required)



Create an `/ai-journey` folder in your repository documenting how you used AI tools.



### Required Files



```

📁 ai-journey/

├── README.md          # Summary of your AI usage

├── prompts.md         # Key prompts you used

└── learnings.md       # What you learned in the process

```



### What to Document



**prompts.md** — Don't document everything, just the interesting parts:



```markdown

## Prompt: Phone number regex

**Tool:** ChatGPT-4



**What I asked:**

"Create a regex to convert Brazilian phone numbers to E.164 format"



**What happened:**

Initial regex didn't handle 9-digit mobile numbers. I had to...



**Final solution:**

[your code]

```



**learnings.md** — Reflect on the experience:



```markdown

## What worked well

- AI was great for boilerplate code

- Helped me explore libraries I wasn't familiar with



## What didn't work

- Initial architecture suggestion was over-engineered

- Had to simplify after understanding the actual requirements



## What I'd do differently

- Start with clearer requirements in prompts

- Ask for simpler solutions first

```



---



## Submission



### Languages



**Python** or **C#** — choose the one you're most comfortable with.



### Repository Structure



```

📁 your-repo/

├── src/                  # Source code

├── tests/                # Tests

├── ai-journey/           # AI documentation (required)

├── docker-compose.yml    # If applicable

└── README.md             # Setup instructions

```



### How to Submit



1. Create a **public** GitHub repository

2. Open an **Issue** in this repository with:

   - Title: `[Backend] Your Name`

   - Link to your repository

   - Brief description of your approach

   - Anything you'd like us to know



### Timeline



- **Recommended:** 7 days

- **Need more time?** Just let us know in the issue



---



## FAQ



What languages can I use?



Python or C#. Choose the one you're most comfortable with.



Are there open positions?



Not always, but we maintain a talent pool. Great submissions stay on our radar for future opportunities.



What if I can only complete part of the challenge?



Submit what you have! Partial submissions with quality code tell us more than complete submissions with poor code. Just document what's missing and why.



Should I include extra features?



Only if they add clear value and don't compromise the core requirements. We prefer well-executed basics over half-finished extras.



How will I know my seniority level?



We don't ask you to self-declare a level. We evaluate your submission across all criteria and determine fit based on our internal standards.



---



## Other Challenges



If you're applying for a front-end position, check out our [frontend-challenge](https://github.com/juntossomosmais/frontend-challenge).



---



## Questions?



Open an [issue](../../issues) or reach out to **vagas-dev@juntossomosmais.com.br**.



Before asking, please check if your question was already answered in [previous issues](../../issues?q=is%3Aissue).



---





  Made with 💛 by the Engineering Team at Juntos Somos Mais