A simple API rate limiter service built with Go, Chi router, and Redis.
This service restricts the number of API requests per user within a given time window using Redis as a counter.

• Rate limiting per user (userId)
• Configurable limit and time window
• Redis-based counters with TTL
• Lightweight HTTP server using go-chi
• JSON response with proper HTTP status codes

• Go (Golang)
• Chi (HTTP router & middleware)
• Redis (in-memory data store)

. ├── main.go # Entry point
├── ratelimiter/ # Rate limiting logic & handlers
│ ├── limiter.handler.go # HTTP handler for /send-data
│ ├── limiter.service.go # Core rate limiter logic
│ └── limiter.interface.go # Request body + constants
└── redis/ # Redis client wrapper
└── redis.go

Make sure Redis is running locally on port 6379: docker run -d -p 6379:6379 redis

go run main.go

Server will start on: http://localhost:8080

Example request: curl -X POST http://localhost:8080/send-data
-H "Content-Type: application/json"
-d '{"userId": "12345", "name": "John Doe"}'

✅ Success: { "status": "data received" }

❌ Rate limit exceeded: { "error": "rate limit exceeded for user 12345" }

• Each user can make up to 3 requests per 60 seconds (RateLimit = 3, RateLimitDuration = 60).
• Counters are stored in Redis using two keys:
  • exp-{userId} → expiration key (marks the time window)
  • incr-{userId} → request counter

Flow:

1. First request → sets both keys (exp with TTL, incr = 1).
2. Subsequent requests increment incr.
3. If incr > RateLimit, return HTTP 429 Too Many Requests.
4. When exp expires, the counter resets.

• Update RateLimit and RateLimitDuration in ratelimiter/limiter.interface.go if needed.
• Requires Redis >= 6.x.
• Logs all connections and errors.

All rights reserved.
This project is for demonstration purposes only.