# Express: preserve requirements through advanced agent edits

- [Reserve stock in Express with one conditional database update](https://frameworkrecipes.dev/express/transactional-reservation/guide.md): Checking stock in JavaScript and then writing a new total permits two requests to reserve the same remaining unit. A conditional UPDATE puts the availability decision into the database statement that changes the row. Parameter binding keeps the SKU out of SQL syntax.
- [stock-never-negative rule pack](https://reporules.fyi/express/transactional-reservation/rule-pack.zip): YAML requirement and agent task.
- [Return the PostgreSQL client after every Express transaction outcome](https://frameworkrecipes.dev/express/transaction-cleanup/guide.md): A transaction helper often looks correct in a successful request while leaking a connection on an exception. Under load the pool exhausts and later requests wait indefinitely. finally covers the paths that normal return statements and rollback handlers miss.
- [transaction-releases-client rule pack](https://reporules.fyi/express/transaction-cleanup/rule-pack.zip): YAML requirement and agent task.
- [Framework rule pack](https://reporules.fyi/express/rule-pack.zip): All requirements from this framework site.