Scaling APIs: Lessons from 0.6B Requests
What I learned building systems that serve 600 million requests monthly with 99.99% reliability at Microsoft.
Serving 600 million requests monthly with 99.99% reliability isn't just about writing good code. It's about building systems that fail gracefully, recover quickly, and scale predictably.
The Reliability Mindset
At Microsoft scale, every decision has consequences. A small memory leak becomes a massive problem. A poorly indexed query brings down entire services. You learn to think in terms of blast radius and graceful degradation.
Key Principles
- Circuit breakers everywhere - Fail fast, recover faster
- Observability first - You can't fix what you can't see
- Gradual rollouts - Never deploy to 100% at once
- Stateless design - Make horizontal scaling trivial
The Human Element
Technology is only half the battle. The other half is building teams that can operate these systems. Clear runbooks, effective on-call rotations, and a culture of learning from failures.
These lessons now inform everything I build at Modulir and Call Card. Scale isn't just about handling load—it's about building systems that humans can understand, maintain, and improve.