I've been running Jenkins on a self-managed k8s cluster for about three years. It worked, but the toil was getting real—plugin conflicts, scaling headaches, and pipeline DSL that only two of us could maintain. Last quarter, we finally pulled the trigger on a full migration to CircleCI.
The primary driver was engineer productivity, but I've got the cost breakdown too. Our team is 12 developers, monorepo with about 300K lines of code, averaging 80 builds/day.
**Why we switched:**
* **Maintenance Overhead:** We were spending ~15 engineer-hours/month on Jenkins upkeep (k8s node issues, plugin updates, credential rotation). That's gone to near zero.
* **Configuration as Code:** Our `config.yml` lives with the repo. Every change is reviewed, versioned, and rollbacks are trivial. No more clicking through Jenkins UI.
* **Native Docker/K8s Support:** No more wrestling with the Jenkins Kubernetes plugin. Defining a container per job is dead simple.
* **Performance:** Our average pipeline time dropped from ~14 minutes to ~9 minutes. The big win was in queue times—Jenkins executors were a constant bottleneck.
**The Numbers:**
* **Previous Jenkins Costs (monthly):**
* AWS EC2 for k8s nodes (c5.xlarge x 3): $210
* EBS volumes: $45
* My rough estimate of 15 engineer-hours at our internal rate: ~$2,250
* **Total (with labor): ~$2,505**
* **Current CircleCI Costs (monthly):**
* CircleCI Plan (Performance, 5 containers): $1,500
* Engineer hours for CI maintenance: < 2 hours (~$300)
* **Total: ~$1,800**
That's a **~28% saving** when you factor in the labor, which is now freed up for feature work. The raw infra cost was only $255, so moving to SaaS obviously increases that line item. But the true cost was hidden in our salary burn.
**Trade-offs we accepted:**
* Vendor lock-in: We're now tied to CircleCI's pricing model and feature set.
* Less granular control: We can't tweak the underlying queue logic or install random plugins anymore.
* Cache management: We had to re-architect our caching strategy, but it's more reliable now.
For our team size and velocity, the switch was a clear win. The ROI was in reduced cognitive load more than direct dollar savings. For larger orgs with dedicated platform teams, the calculus might be different.