What I learned building a workflow engine from scratch in Rust

About 2 years ago, I needed a way to run a handful of tasks reliably: validate an order, charge a card, check inventory — in parallel where possible, with retries, and crash recovery. That's it. So I evaluated Temporal. Spun up the server cluster, read the SDK docs, then hit the first wall: a whole complex framework to learn, a platform to understand and heavy investment.. I moved on to Airflow — wrote a DAG file, set up the scheduler, the webserver, the metadata DB, just to run three functions. I looked at Celery, Prefect, Step Functions. Each time, I was paying an infrastructure or complexity tax that felt wildly disproportionate to what I actually needed. So I built my own: Sayiir . This post isn't a pitch for it — it's the five design decisions I wrestled with and what I landed on. If you've ever been curious about what goes into a workflow engine, or if you're building something similar, maybe this saves you some wrong turns. Decision 1: How do you represent a workflow? The first