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I Migrated 50K Lines of Java Spring Boot to Rust in 3.5 Months: 87% Cost Reduction
Our $47K/month AWS bill was killing our startup. I rewrote 50,000 lines of Java Spring Boot to Rust Actix over 3.5 months. Result: $6K/month bill, 12× throughput, 87% faster response times. Here’s exactly how we did it — code included.
The 3 AM Wake-Up Call
3 AM. Slack notification. AWS bill: $47,000. Again.
I’m sitting in my home office. Cold coffee. One monitor open to CloudWatch graphs that look like a heart attack.
Our Spring Boot services are bleeding money faster than we can raise it.
We have 5,000 daily users. A 6-person team. And an AWS bill that assumes we’re Netflix.
The math is simple. At this burn rate, we don’t reach profitability. We reach zero.
So I proposed something insane.
A full rewrite. All 50,000 lines. In Rust.
My co-founder stared at me for a long second.
“The crab language?”
Six months later, we’re running on 13% of our original infrastructure.
This is how we did it. And why you might want to. Or absolutely shouldn’t.
