We Deleted Tokio from Our Payment System and Cut Cloud Costs by $127,000

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Three months ago, I made a decision that could have gotten me fired.

Our Rust microservice was bleeding money. AWS bills climbing every month. Latency creeping up. The team was adding more instances, more memory, more everything. Classic scaling problem, right?

Wrong.

I spent a weekend ripping out our entire async runtime. Deleted Tokio. Replaced futures with plain threads. Went back to blocking I/O like some dinosaur writing C code in 1995.

Monday morning, I deployed it to production.

The Slack channel went silent. Then the metrics started coming in.

Memory usage down 42%. Response times improved across every percentile. P99 latency dropped from 340ms to 180ms. The cost projections showed we’d save over $127,000 annually.

My manager asked me one question: “Why didn’t we do this sooner?”

Good question.

The Async Lie We All Believed

Let me take you back to when I first learned Rust. Every tutorial, every blog post, every conference talk had the same message: async is the future. Tokio is essential. If you’re not writing async code, you’re stuck in the past.