LLM API Resilience in Production: Rate Limits, Failover, and the Hidden Costs of Naive Retry Logic
· 10 min read
In mid-2025, a team building a multi-agent financial assistant discovered their API spend had climbed from $127/week to $47,000/week. An agent loop — Agent A asked Agent B for clarification, Agent B asked Agent A back, and so on — had been running recursively for eleven days. No circuit breaker caught it. No spend alert fired in time. The retry logic dutifully kept retrying each timeout, compounding the runaway cost at every step.
This is not a story about model quality. It is a story about distributed systems engineering — specifically, about the parts of it that most LLM application developers skip because they assume the provider handles it.
They do not.
