In large-scale financial systems, correctness isn't optional. Systems don't just need to be fast—they must be provably safe.
One of the most critical lessons I learned was how to build fail-safe architectures that emphasize:
- Immutable audit trails
- Deliberate failovers (not just HA failover scripts)
- Redundant state checks and transaction guards
These experiences taught me to see failure scenarios before they occurred—and to design systems that could fail gracefully under real-world stress. It's a skill I still lean on heavily in designing high-reliability backend systems today.