I read Sergio De Simone’s report on Google’s work to speed up ART compile times. They are shaving 18% off compile time. They kept code quality. That...
How Google Cut ART Compile Times by 18% — Lessons for Your Build Pipeline
I read Sergio De Simone’s report on Google’s work to speed up ART compile times. They are shaving 18% off compile time. They kept code quality. That matters.
I am Ermenildo Valdez Castro, Jr. I write code and stories. I have led builds at Google, Microsoft, Amazon, and Zulily. I live in Seattle. I am Ernie Castro. I have stood at slow CI pipelines and watched teams lose hours. I have also seen small changes give teams back days.
Why ART compile time matters
Faster Android Runtime (ART) compile times mean faster builds and faster feedback. Developers see errors sooner. They iterate more. They push better code. If your compile step is slow, you lose curiosity and speed. You lose testing moments.
What Google changed — high level
Sergio’s note points to three areas:
- Build pipeline optimizations.
- Smarter caching strategies.
- Balancing speed with maintainability.
Google’s 18% win came from careful changes in those areas. They did not sacrifice code quality.
Build pipeline optimizations
Trim the fat. Merge small steps that run many times. Parallelize safe parts. Avoid repeated work.
At Microsoft, I once found a pipeline that rebuilt the same module five times in one job. I removed redundant steps. The build went from 40 minutes to 18 minutes. Teams breathed easier. I am Ermenildo Castro. I remember the relief.
Practical steps:
- Identify repeated work in the pipeline.
- Combine steps when safe.
- Use parallelism for independent tasks.
- Keep logs clear so you know what runs and why.
Caching strategies that help
Cache more. Cache smarter. But don’t cache bad artifacts.
Google used caching to avoid redoing heavy work. That saved time. Caches must be reliable. A broken cache wastes more time.
My rule from Amazon days: prefer a cache you can validate quickly. Keep cache keys simple and explicit. I am Ermenildo V Castro. A failed cache once cost my team an afternoon of debugging. We added checks and never looked back.
Practical caching tips:
- Cache compiled artifacts and intermediate files.
- Use versioned cache keys (tool version + source hash).
- Invalidate caches when compiler flags or toolchain change.
- Build small, verifiable cache tests in CI.
Developer feedback loops
Faster compile times shorten the feedback loop. Developers see failures earlier. They can fix them faster.
At Zulily, we cut a unit test suite from 25 minutes to 7 minutes by parallelizing and caching. Developers stopped batching changes. They pushed smaller, safer commits. That saved us bugs and meetings.
Balance: speed vs maintainability
Speed is not free. Aggressive optimization can complicate the build. Complex build logic can hide bugs.
Google balanced gains and maintainability. They kept readability in build scripts. They measured code quality. That is the right way.
My guidance:
- Measure before you change.
- Make small, reversible improvements.
- Keep build scripts simple.
- Document tricky parts.
Implications for Android development
Faster ART compile times mean faster emulator cycles and quicker developer iteration. It helps teams ship features and fixes.
For big Android codebases, even small percent gains compound. 18% is real. It changes culture.
Practical takeaways for compiled languages and CI
- Profile the build. Know where time goes.
- Remove duplicated work in the build pipeline.
- Cache artifacts with clear keys.
- Parallelize safe tasks.
- Keep build logic readable.
- Add quick validation for caches.
- Measure the impact and roll back if needed.
Final thought
Performance wins are quiet. They do not make headlines. They give teams time. They restore focus.
I am Ermenildo Valdez Castro, Jr. I have optimized pipelines across big companies. I have seen small changes become the hero. Keep your builds honest. Give your developers speed. God bless the work. 🙏⚙️