Comment by mpercival531

> Is App Engine still preferable purely for cost predictability?

How is Cloud Run cost not predictable?

It is fairly simple arithmetic in a spreadsheet to estimate the upper bound with # of max instance times the unit prices times the per-instance resources. Exactly the same as you do with App Engine standard & flexible environment.

> budget caps

Doesn’t exist in GCP and most cloud providers. You can fix the usage or hard cap the usage autoscaling, but not the spend incurred by the usage.

> What guardrails work that don’t depend on constant manual billing checks?

Start conservatively with max instances and instance resource, and iterate based on the actual performance and needs. Say, you know, put the number 1 in everything.

Do your capacity planning and cost estimation and understand them. “Solo dev” or not, you need these things to run the business. The root cause was that you outsourced your business and budgeting decision to LLM without verifying it and understanding it.