API response compression with Rack::Deflater

Large JSON payloads consume bandwidth and increase latency, especially for mobile clients on slow connections. Rack::Deflater middleware automatically compresses responses using gzip when clients send Accept-Encoding: gzip headers. This typically reduces payload sizes by 70-90% for JSON, dramatically improving transfer times. The middleware is smart enough to skip compression for small responses where overhead exceeds benefit, and it respects already-compressed content types like images. The CPU cost of compression is negligible compared to network transfer time savings. I configure deflater early in the middleware stack so it wraps the entire response, and I verify compression with browser dev tools or curl with verbose output.