Case Study: Circle

There’s a reason CRON is still around: it’s predictable. And yet in modern infrastructure stacks, teams build "just enough" scheduling into sidecars, queues, even CI runners — and forget they now own distributed orchestration.

This case study explores:

• how ad-hoc schedulers emerge inside microservices

• why observability is a lie if your retries are infinite

• what happens when your rate limiter resets on deploy

• and how to debug a job that 'ran successfully' — but didn’t do anything.

We’ll look at:

- Real-world postmortems from Kubernetes Jobs and sidecar queues

- Strategies to enforce SLAs without polling

- Why idempotency doesn’t save you when jobs run twice after a clock skew

TL;DR:

Schedulers are infrastructure. If you build one by accident — document it, alert on it, and assume it will fail.