How can you optimize a slow Gradle build?

Slow Gradle builds usually trace back to a small set of repeatable causes, each with a fairly direct fix.

1. Enable the configuration and build caches — skips both re-evaluating scripts and re-running tasks with unchanged inputs.
2. Enable parallel execution (org.gradle.parallel=true) so independent modules build concurrently instead of strictly sequentially.
3. Avoid unnecessary eager configuration — use lazy tasks.register and the Provider API instead of eagerly resolving values during configuration.
4. Tighten dependency configurations (implementation vs api) so changes in one module don't force unnecessary recompilation of unrelated downstream modules.
5. Increase daemon JVM memory via org.gradle.jvmargs if builds are memory-constrained and spending time on GC.
6. Profile with a build scan (--scan) to actually see which tasks dominate build time, rather than guessing.

The general order of operations: profile first with a build scan, then apply caching/parallelism (usually the biggest wins for the least effort), and only after that look at restructuring dependency configurations or splitting modules further.