Susan, a software developer, wants her web API to update other applications with the latest information. For this purpose, she uses a user-defined HTTP tailback or push APIs that are raised based on t

Web shells are malicious scripts uploaded to compromised web servers by attackers to maintain persistent remote access and execute commands - they are an offensive security tool, not a legitimate data-push mechanism.

A webhook is a user-registered HTTP endpoint that a server calls automatically when a defined trigger event occurs, delivering data to the receiving application instantly without polling - this matches Susan's requirement exactly. The question's own description ('user-defined HTTP callback or push API raised based on trigger events that supplies data to other applications in real time') is a near-verbatim definition of a webhook. Webhooks are a standard pattern for real-time event-driven integrations between web services.

REST API is a client-pull architectural style where the client initiates each request to retrieve data from a server - it does not natively push data to other applications based on server-side trigger events.

SOAP API is a client-initiated, protocol-based messaging standard using XML that requires the client to send a request before the server responds - it is not event-driven or push-based.