Crypto Observability API (Backend)

Backend service for the Crypto Observability project, built with FastAPI. This API aggregates and exposes cryptocurrency market data (via CoinGecko) and is designed with clean architecture, strong typing, and production-ready practices.

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Tech Stack

• Python 3.11+
• FastAPI
• Uvicorn
• Pydantic
• HTTPX (external API client)
• JWT Authentication
• Redis (cache)
• PostgreSQL (optional, persistence)
• Pytest
• Ruff (linter)
• Black (formatter)
• direnv (optional, local environment automation)

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Project Goals

• Fetch and normalize crypto market data
• Measure external API performance (latency, errors, availability)
• Expose secure endpoints for a frontend dashboard
• Handle authentication and authorization via JWT
• Provide a clean, production-ready backend architecture

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Environment Setup

Requirements

• Python 3.11+
• pip
• direnv (optional but recommended for local development)

⚠️ This repository includes a versioned .envrc file. If you have direnv installed, you only need to run direnv allow once.

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Virtual Environment Management (direnv)

This project uses direnv with layout python3 to automatically create, activate, and deactivate a Python virtual environment.

The virtual environment lifecycle is handled by direnv when entering or leaving the project directory.

The .envrc file is already versioned in this repository.

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Using direnv (Recommended)

Install direnv (Ubuntu):

sudo apt install direnv

Ensure the direnv hook is enabled in your shell (.bashrc).

After cloning the repository, run:

direnv allow

From this point on:

• Entering the project directory automatically creates and activates a virtual environment
• Leaving the directory automatically deactivates it
• No manual virtual environment creation is required

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Manual virtual environment (without direnv)

If you prefer not to use direnv, you can manage the virtual environment manually:

python3.11 -m venv .venv
source .venv/bin/activate

In this case, you can safely ignore the .envrc file.

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Install Dependencies

pip install -e ".[dev]"

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CoinGecko API Key (Recommended)

To reduce 429 Too Many Requests responses, configure one of the following:

• COINGECKO_PRO_API_KEY (preferred when available)
• COINGECKO_DEMO_API_KEY

Example:

export COINGECKO_DEMO_API_KEY="your-demo-key"

If both are set, the API uses COINGECKO_PRO_API_KEY.

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Run the Application

uvicorn app.main:app --reload

API will be available at:

http://127.0.0.1:8000

Interactive docs:

• Swagger UI: /docs
• ReDoc: /redoc

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Linting and Formatting

ruff check .
black .

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Testing

pytest

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Git Workflow

This project follows Conventional Commits:

• feat: new features
• fix: bug fixes
• chore: tooling / maintenance
• refactor: code refactors
• test: tests only

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License

MIT