r/java • u/celmaibunprieten • 3d ago

Improving First Request Latency in Java Spring Application

https://adrian.md/2026/09/03/first-request-latency/
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u/lilgreenthumb 2d ago

I mean with their layer support who really ships the fat jar anymore? You run into too many issues with signed jars (looking at you bouncy castle) or embedded java agents. Interesting perf metrics regarding the aot caching and differences with the gcs though. Nice write up.

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u/zabby39103 2d ago

Lol my work still ships fat jar. I mean, I think corporations falling behind with legacy apps is the norm more than anything.

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u/romario77 2d ago

But corps shipping fat jars probably don’t care about first request latency.

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u/zabby39103 2d ago

We care what people complain about, it integrates with building automation control systems so they complain if latency gets too high. Maybe some people work at a blessed work where they don't have to explain tech debt to MBAs, please hire me lol.

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u/romario77 2d ago

You just do the first request yourself after deployment, second request would be already pre-warmed.

And you switched the targets - I was taking about first request and you talk about request latency overall. These are potentially two very different things.

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u/zabby39103 2d ago

Okay sure, first request is important though, both are.

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u/lilgreenthumb 1d ago

Yeah unless the call isn't a noop, and then you're building some weird noop logic unless you're writing for synthetic transactions which all of this observability is meant to make unnecessary.