How Youku Cut Android Build Times by Up to 35 Minutes: A Deep Dive

Background

Android projects typically use Gradle for building, but its slow execution has long been a pain point. At Youku, the rapid growth of features and codebase caused full‑package build times to reach 35 minutes, severely impacting integration and iteration efficiency.

Metrics and Goals

The team defined core metrics—build duration, failure rate, and hourly build count—to evaluate optimization impact. Monitoring showed high‑cost tasks and unreasonable build configurations as the main culprits.

Optimization Strategy

The effort was split into three dimensions: data‑metric definition, technical optimization (software + hardware), and result preservation.

Software Optimizations

Remove Atlas framework from the build side, eliminating its complex build steps and reducing debug build time by ~3 minutes and release build time by 4‑5 minutes.

Upgrade Gradle (4.4 → 5.5) and Android Gradle Plugin (3.0.1 → 3.4.3). Benefits came from newer AAPT2/ProGuard, better task parallelism, and asynchronous configuration loading, shaving ~2 minutes from debug builds and ~4 minutes from release builds.

DX build tuning: set

android.dexingNumberOfBuckets=16</code><code>android.dexingWriteBuffer.size=256</code><code>android.dexingReadBuffer.size=256

to increase cache size and reduce I/O, cutting both debug and release builds by ~3 minutes.

Eliminate redundant tasks (e.g., postPackageDebug, remoteSignAppDebug, DexCountDebug, etc.) to avoid unnecessary APK unpack‑pack cycles, saving 15 seconds to 20 seconds per build.

Hardware Optimizations

Performance profiling with iostat and tsar revealed severe CPU I/O‑wait during builds. Switching from mechanical disks to SSDs reduced I/O bottlenecks, cutting debug build time by ~5 minutes and release build time by ~10 minutes across various machine groups.

Pipeline Redesign

By consolidating post‑processing steps into a low‑copy, single‑extract‑single‑compress pipeline, the team reduced APK handling overhead, achieving an additional ~21 seconds for debug and ~11 seconds for release builds.

Results

Combined optimizations lowered Android debug build time from 12 minutes to 2.5 minutes and release build time from 35 minutes to 12 minutes. Additional fine‑tuning yielded further reductions of seconds to minutes across various stages.

Future Work

Control and clean ProGuard/R8 rules to avoid unnecessary obfuscation overhead.

Address code‑base decay by removing dead code and improving modularity.

Further R8 optimizations once upstream bugs are resolved.

The Youku team will continue to monitor and improve build performance, inviting community feedback.