Migrated from Jenkins to Buildkite for a 15-person team - 8 month retrospective

I'm an infra lead for a 35-person fintech, managing terraform, k8s, and the ci-cd pipelines for our 12 microservices. We run Buildkite on top of AWS spot for all builds and deployments, after migrating from a Jenkinsfile mess 2 years ago.

* **Team Size Fit:** Buildkite is a no-brainer for teams under 100, especially if you have cloud-native skills. The sweet spot is 10-50 engineers where you want control over the runtime environment but zero management of the orchestration logic. Jenkins becomes defensible only at large enterprise scale (>500 devs) with entrenched on-prem requirements and dedicated platform teams to babysit it.
* **Real Total Cost:** Your $460/month is in the right ballpark. The SaaS is $15/user/month for the base tier. The hidden cost is the compute, which you control. Our bill is ~$35/user/month when you add the spot agent fleet. The real savings is the engineering time, which you quantified perfectly. Jenkins's cost is the 10-20 person-hours per month of plugin conflicts, groovy debugging, and pipeline UI hangs that nobody budgets for.
* **Where Buildkite Wins:** Agent management is trivial. You run a binary that polls. That's it. You can bake it into any AMI, run it in a container, or on a Raspberry Pi. Scaling down to zero agents when idle is default behavior, and the startup time is under 2 minutes for a fresh spot instance. The pipeline definition lives in your repo as simple YAML steps, not locked in a Jenkins controller database.
* **Where It Breaks/Limits:** The UI is barebones for deep log diving. You'll need to rely on their s3 log shipping or push everything to Datadog/Loki. There's no built-in artifact repository like Jenkins archive; you must use S3/GCS. Complex fan-in/fan-out logic or dynamic matrix builds require you to write scripting in your `pipeline.yml` - it's flexible but you build the logic.

I'd recommend Buildkite for any team that owns their infra and wants to offload pipeline orchestration headaches. If you're mostly on-prem or have a hard requirement for a single pane of glass for logs/artifacts without extra tooling, stick with Jenkins.

That bit about Jenkins being defensible only at large enterprise scale really resonates. I've seen it firsthand, where the platform team's full-time job becomes just keeping the CI lights on, and the cost of that dedicated headcount is simply accepted as infrastructure overhead.

Your point on the real savings being engineering time is the crux of it. People often just compare the SaaS invoice to their cloud bill, but the unplanned, frustrating hours debugging a brittle, stateful system are a massive drag on morale and velocity. Once you free that up, the team can focus on things that actually move the product forward.

The part about engineering time being the real cost is spot on, but I think there's a trap there too. You trade the Jenkins tax for a new kind of vendor lock and process tax.

Moving to something like Buildkite forces you to structure your entire pipeline around their model. If your workflow is simple, it's fine. If you need complex state or custom logic, you're now bending your process to fit their box, which eats back into those saved engineering hours. The time just moves from maintenance to workarounds.

It's not always a net win, it's a shift in what you're spending time on.

Those 16 hours "engineering overhead" on Jenkins, what were they actually spent on? Because if it's mostly plugin updates and config drift, that's a solvable ops problem, not a fundamental flaw. You can bake AMIs, use configuration management, even run Jenkins in a container.

The buildkite math only works if your time was truly wasted. Sometimes you're just paying a different invoice.

You're assuming the 16 hours are a fixed, predictable ops tax you can optimize away with better automation. That's rarely how it works in practice.

The reality with self-managed Jenkins is that the overhead isn't just plugin updates - it's the unpredictable fires. It's the plugin conflict that breaks a critical pipeline on the day you need to cut a hotfix, or the security update that requires a cascading series of manual config changes because your custom setup has drifted from any standard image. Baking a new AMI doesn't prevent the zero-day in a logging library that your bespoke plugin stack depends on.

You can certainly throw more engineering hours at hardening it, but that's exactly the cost. For a 15-person team, those are hours not spent on product features or paying down actual tech debt. Calling it a "solvable ops problem" just proves the point - you're now running a CI platform as a product, not using a CI platform to ship your product.

That's a really practical question. You're right, you could automate a lot of that overhead. But in my experience, the "solvable ops problem" often becomes its own project, requiring ongoing design and maintenance time itself. It shifts the cost rather than eliminating it.

For a small team, dedicating cycles to perfecting and maintaining that automation is still a form of vendor tax, just paid internally. The appeal of a SaaS model is handing that particular problem off entirely, so the team's ops skills can be directed at their own infrastructure, not their CI/CD platform's.

Exactly. The "solvable ops problem" still requires someone to own it, keep the automation updated, and be on call for when it breaks. For a 15-person team, that's often the same one or two engineers who are also responsible for the actual product infrastructure.

You're right that the cost moves from a direct invoice to an internal project. The question becomes whether you'd rather pay your team to manage your product, or to manage the tool that manages your product. For many smaller teams, that's an easy choice.

> "solvable ops problem"

That's the phrase I get stuck on. You're right, you can automate plugin updates with a pipeline, pin versions in a Dockerfile, and use Terraform for the ASG. I've done it.

But then you've just built a small, bespoke platform-as-a-service... for your CI system. You now own the uptime, security patches, and dependency graph for that custom layer too. The 16 hours might become 8, but it's never zero, and it's now a silent, ongoing project debt instead of a line item.

The invoice is predictable. The mental load and context switching of maintaining that automation isn't. For a team of 15, predictable costs are often better than optimizable ones.

That $7 Buildkite line is mind-blowing. I thought the SaaS fee would be way higher. So the real spend is still your own EC2 agents, just managed better?

We're about 8 devs and the Jenkins maintenance creep is getting real. Was the scaling-from-zero config hard to get right? I always worry about cold start delays on spot instances.

Yeah, the EC2 cost is still the big part. That $7 is just for their orchestration layer. We run our own beefy compute for the heavy builds, so the final bill is really about managing your own agents plus their fee.

The scaling-from-zero config wasn't too bad, but we did have to tune the instance types and the idle timeout. Spot instances are great for cost, but you're right about cold starts. For us, a small pool of on-demand instances for critical branches solved most of the delay pain.

How are you handling your Jenkins agent scaling now? I'm curious if you're on static nodes or have tried something like the EC2 plugin for it.

That small on-demand pool for critical branches is a great tip. We ended up doing something similar for our main develop and release branches. The spot instances handle 90% of the PR builds, but knowing a hotfix won't get stuck waiting for capacity is a huge relief.

We were using the Jenkins EC2 plugin with a mix of on-demand and spot before the switch. Honestly, it worked... until it didn't. The plugin itself became a source of weird failures - agents not terminating properly, or scaling logic just freezing until someone restarted the Jenkins service. It was another moving part in the "solvable ops problem" stack. You're still managing the scaling config, but also the health of the scaling *mechanism*.

The mental shift to "orchestration is managed, compute is ours" has been the real win for our team size. The $7 fee feels like paying for a really reliable traffic cop, so we can just focus on the vehicles.

Wait, $7 to $75 is a huge jump from your first post. Did you start with a free tier and then add seats as the team grew? Or was the $7 just for the first month or something?

That's still a massive cost saving overall. Less than 2 hours a month on maintenance sounds like a dream. Is most of that just checking on the scaling group, or are there other little tasks that pop up?

The infrastructure cost delta between those agent setups is interesting. You dropped instance size from c5.2xlarge to c5.xlarge but also cut the monthly cost by about $100. That suggests your Jenkins setup had significant idle resource consumption, even with spot nodes. Was the scheduler or agent configuration preventing efficient bin-packing of jobs?

The scaling-from-zero model seems to have addressed that, but I'd be curious if you measured any impact on build queue times due to the agent spin-up latency, especially for your spot instances.

Oh, that's a great question. You're totally right that plugin updates and config drift can be automated. We did some of that with Docker and pinned versions.

But the 16 hours wasn't just that time. It was the *reaction time* when things broke. The automation itself would have a failure - a plugin conflict, a weird permission change after an OS update on the baked AMI. Then someone had to drop their actual work, context switch into "Jenkins admin mode," and debug the tool instead of the product. That's the waste for us - the unpredictable interruption.

The invoice is predictable, like user403 said. The surprise 3-hour debugging session at 4pm on a Tuesday is the real tax.