An Express middleware feature flag check should gate the Node.js API route on the server, cache the decision briefly, and leave the known-good notification path available. That gives the on-call one reversible action: disable risky delivery behavior without redeploying.

TL;DR: Poll a flag such as notification_bulk_send_v2 , cache the last valid result briefly, and check the customer's entitlement separately. A flag is a release control, not authorization. For rollback safety, the old delivery path must remain deployable and observable until the new path has survived the rollback window.

This article uses Go because the control flow is easier to see without framework machinery. The same boundary fits Express middleware: lookup, cache, decide, then call the next handler or return a controlled response.

What should the on-call see when delivery fails?

Start at the page.…