AI Agents Can Now Optimize Your Slow Java Code: A Spring Boot Workflow That Used to Need a Specialist

Last week a tweet went viral claiming that people complaining about LLM-generated bloat would "eat crow" once everything gets rewritten in hand-optimized assembly. Dan Luu, the engineer behind some of the most cited performance writing on the internet, responded with an essay titled "There's no reason for software to be slow anymore." It hit 620 points on Hacker News in about a day, and its argument should change how every Java team spends its next sprint. The core claim is simple and backed by real experiments: performance work that used to require a rare specialist can now be done by anyone who can type a few sentences. Luu quantifies it. The human-time cost of an optimization has dropped by what he calls "frequently 1000x / 10000x / 1000000x." He had an agent do workload-specific optimization of his own ripgrep usage, and launching it took about 2 minutes of his time. Jamie Brandon, a strong performance engineer, took Anthropic's public performance takehome exercise, then let Claude pick up where he left off. Claude got a much better result. Looking at the diff, Brandon said some of the agent's optimizations were things he had thought of but not gotten to, and others were, in his words, "just crazy shit that I would never try unless I was working on this for weeks." If you have spent six years writing Spring Boot services like I have, your reaction is probably the same as mine: interesting for regex engines, but what does this mean for the average enterprise Java service? The honest answer is that most of us will never need a custom JIT. But the underlying shift, that measuring and trying an optimization now costs minutes instead of days, applies directly to the slow endpoints every real codebase accumulates. This article is a practical workflow for turning an AI agent loose on a slow Spring Boot hot path without letting it ship garbage. Full disclosure up front: the numbers I cite from Luu's essay are his experiments, not mine. The workflow below is the one I no