Monorepo CI at Scale: Bazel Caching for 1,000 Microservices

Imagine for a moment you're tasked with managing not just a few, but a thousand microservices.

And they're all living together in one single repository.

Sounds incredibly daunting, right?

Oh, absolutely.

Because at that kind of scale, the traditional approaches to continuous integration, what we all know as CI, they don't just struggle, they completely fall apart.

We're talking about CI pipeline runs that stretch into hours, grinding development to a, well, a screeching halt.

Your team is just waiting, twiddling thumbs, completely blocked.

So today, we're taking a deep dive into precisely this challenge.

How do you engineer a robust, high-performance CI pipeline capable of handling a massive monorepo, one containing thousands of microservices? And this isn't just some theoretical problem for a thought experiment.

It's a very real, very pressing issue for some of the world's largest and most innovative tech companies.

They're solving it, and we're going to unpack how.

And that really gets to the core of the problem, doesn't it? If you look at most changes to a code base, even one of this enormous size, they typically affect only a tiny fraction of it.

We're

often talking less than maybe 5% of services at any given time.

Yet, without real intelligence built into the system, most, well, naive CI setups will rebuild and retest everything on every single commit.

So our deep dive today is all about achieving what we call surgical precision in your CI, moving far beyond that brute force, you know, wasteful approach.

Okay, so our mission today is to show you exactly how to achieve that.

We'll be exploring a powerful combination of tools and strategies.

Bazel is the build orchestrator, coupled with powerful remote caching and intelligent selective testing.

Mini

pieces.

Exactly.

The goal, to fundamentally transform CI from being that dreaded bottleneck that slows everyone down into a true competitive advantage that actually accelerates development velocity.

Okay, let's unpack the immediate pain points of traditional CI at this scale, because they are truly brutal.