How I solved Ethereum RPC rate limits with traffic engineering instead of paying $250/month

A production engineering story about rate limits, retries, failure behavior, and building RPC traffic control At some point our backend started failing. Not completely. Not catastrophically. Just small strange things: a cron job running longer than usual random RPC failures occasional timeouts rare stuck executions Nothing dramatic. But enough to feel dangerous. If you've worked with distributed systems — you know this pattern. Systems rarely explode. They slowly become unreliable first. And this story is about how a simple wallet balance collector turned into an RPC infrastructure problem… and why the real solution wasn't buying a bigger plan. The original problem was simple We needed to collect wallet balances to display user positions. Nothing unusual. Architecture was basic: cron (every 15 min) ↓ fetch balances from blockchain ↓ store results Each execution made around 30–50 RPC calls , mostly: eth_call Stack: NestJS backend ethers.js standard RPC providers Everything worked perfec