Scaling Your SaaS Infrastructure: Lessons from 50M API Calls/Day

When we hit 10 million API calls per day, our infrastructure started showing cracks. Database queries that took milliseconds started taking seconds. Response times crept up. Alerts fired more frequently.

The journey from 10M to 50M daily API calls taught us invaluable lessons about distributed systems, caching strategies, and the importance of observability at scale.

Our first major change was implementing a multi-layer caching strategy. We added Redis clusters for hot data, CDN caching for static responses, and application-level caching for computed results. This alone reduced our database load by 60%.

Connection pooling and query optimization were next. We rewrote our most expensive queries, added strategic indexes, and implemented read replicas for analytics workloads that didn't need real-time consistency.

The most important lesson? Invest in observability before you need it. Having comprehensive metrics, distributed tracing, and structured logging made it possible to identify and fix bottlenecks quickly as they emerged.