Your customers write the functions; you run them anyway

Your SaaS ships automations: customers write small scripts that run when their data changes. Customer code is the scariest input a product accepts: so before a script is saved, one request runs every validator against it: syntax, TypeScript, dependencies, magic comments. What passes gets stored; what fails comes back with reasons.

Accepted scripts run in serverless mode: a fresh VM per execution, no state visible from one run to the next, one tenant's script never sharing memory with another's.

Building this yourself means a sandbox service, a queue, and a security review. Here the validator is an endpoint and the isolation is a mode.