<strong>Intro</strong>
Google says Android Runtime (ART) compile times dropped by 18% while keeping code quality intact. That is the headline. It matters...
How Google Cut ART Compile Time by 18% — Faster Builds, Same Code Quality
Intro
Google says Android Runtime (ART) compile times dropped by 18% while keeping code quality intact. That is the headline. It matters. Faster compile times mean faster iteration. Faster iteration means better apps shipped sooner.
Why this matters
Build and compile time is a tax on engineering teams. It slows feedback. It kills momentum. I learned this the hard way at Microsoft, Amazon, and Zulily. Long builds break focus. They make small changes expensive. An 18% improvement is not trivial. It is time back for engineers. It is time back for product.
What Google likely changed (and what you can learn)
Google did not publish every line of code. But improvements of this size usually come from a few places:
- Better parallelism. Use threads well. Let CPUs do real work at once.
- Smarter caching. Avoid repeat work. Cache artifacts and reuse them.
- Reduced I/O. Disk is slow. Cut reads and writes where possible.
- Incremental compilation. Only compile what changed.
- Heuristics and tuning. Make the compiler choose smarter defaults.
- Profile-guided optimizing. Use real runtime profiles to speed compile decisions.
I saw each of these in action. At Zulily I cut a test suite time by reworking I/O. At Amazon I reclaimed minutes by fixing a cache miss pattern. At Google, similar wins scale to millions of devices.
How they kept code quality
Faster compile time must not mean worse output. Quality stayed the same. That means they validated. They ran tests. They measured performance and correctness. Compiler teams use regression suites, bisecting, and staged rollouts. If you want safe speedups in your project, follow this pattern:
- Build a regression test suite.
- Run comparisons: old vs new artifacts.
- Use feature flags and staged rollouts.
- Automate checks in CI.
My memory: once at Google, we bumped compile speed and almost broke a subtle optimizer. Tests caught it. We rolled back. We fixed the bug. We released again. Short story: trust tests more than optimism.
Practical tips to speed up your builds today
- Cache aggressively. Use artifact caches and avoid rebuilding unchanged pieces.
- Parallelize what matters. Measure before you add threads.
- Reduce I/O and temp files. Use tmpfs for heavy temp work if safe.
- Adopt incremental builds. Small changes should be cheap.
- Profile your compiler. Find hotspots. Fix the low-hanging fruit.
- Add a fast path and a full path. Compile fast for development, compile slow for final release.
Keywords developers should care about
Android Runtime, ART compile times, compiler performance, build times, incremental compilation, cache, parallel compilation, profile-guided optimization.
A short personal note
I am Ermenildo V Castro. I worked on big systems at Google, Microsoft, Amazon, and Zulily. I learned to value minutes. I learned to guard quality. Once, a single extra second in build time cost me a full hour across a day. I do not forget that. I write this to help you ship faster. 🚀
Closing
An 18% improvement is a win. It is a reminder that small compiler work gives big returns. Do the small cleanups. Measure. Test. Ship.
Call to action
If you run Android builds, check your cache and parallelism first. If you want a checklist or a short script to profile your compile, say the word. — Ernie Castro 😊