Currency Converter API

A high-performance currency conversion API built with ASP.NET Core, Redis, ELK, and external exchange rate providers.

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🚀 Setup Instructions

Prerequisites

• Docker

1. Clone the repository:

   git clone https://github.com/your-org/currency-converter.git
   cd currency-converter

2. Start app

   make currency

3. Close app

   make stop

4. Explore API

Assumptions Made

• 🔁 Frankfurter API is always available and responds within acceptable latency bounds.
  The system uses retry and circuit breaker policies, but it's assumed downtime is rare and short-lived.

• 💰 Exchange rates do not change more frequently than once per day.
  Caching is based on this assumption to reduce API pressure.

• ⛔ Currencies TRY, PLN, THB, and MXN are considered restricted for business or compliance reasons.
  Any request involving these currencies is treated as invalid.

• 📅 Historical exchange rates are only required from the Frankfurter API's supported range.
  No data transformations or corrections are applied for missing or partial data.

• 🌐 All operations are performed in UTC.
  The system assumes clients either use UTC or convert to/from it on their side.

• 🧪 JWT tokens are trusted and already validated before reaching the endpoint logic.
  Token validation and RBAC are assumed to be handled at middleware level.

• 📦 The caching layer (e.g., Redis) is operational and used consistently across requests.
  If the cache fails, the fallback is to re-query the external provider.

• 🔐 Rate limiting is configured per client (e.g., by ClientId in JWT) and not globally.
  This assumes fair usage distribution among multiple consumers.

• 🔎 Pagination for historical data assumes valid date ranges and sane page sizes.
  No internal guardrails beyond basic validation are in place for absurd requests (e.g., 50 years of data in one go).

• 🏗️ Deployment environments (Dev, Test, Prod) have consistent configurations apart from secrets and URLs.

📈 Possible Future Enhancements

1. Dynamic Configuration via Consul
   Integrate Consul or another configuration provider to allow real-time updates of application settings without requiring application restarts.

2. Microservice Separation
   Decouple authentication and authorization logic from the currency conversion API.

3. Asynchronous Caching with Kafka & Background Workers
   Introduce Kafka as a message broker and implement background worker services to asynchronously update and maintain the cache.

4. Load and Stress Testing Automation
   Implement automated load and stress testing (e.g., using k6, Artillery, or Locust) to validate API performance under high traffic.