Function Request Flow

To understand how Twilio Functions works, first review the HTTP request flow and how Twilio executes your code. Twilio Functions handles most web-app infrastructure so that you can focus on application logic. This process starts at the front door—handling the incoming HTTP request—and continues through the pipeline to your Function code.

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1. An HTTP client sends a request to your Function. For most Functions, the client is the Twilio Voice or Messaging API responding to an incoming phone call or text message.
2. The Twilio Functions Gateway receives this request and attempts to validate it. If your Function has Signature Validation enabled, the Functions Gateway will attempt to validate the signature. If the request or the Twilio Signature are invalid, the request is rejected with an HTTP 400 response.
3. After the Functions Gateway accepts the request, it normalizes the request into a payload for your Function. The normalized request is provided to your Function as two arguments: context and event. Once the payload has been constructed, it is used to invoke your Function.
4. At invocation, your Function begins executing the handler code that you have provided. When your Function completes executing, it can emit a response using the callback method. The emitted response will be transmitted to the Function Gateway.
5. After your Function returns a result, the Functions Gateway constructs an HTTP response and returns it to the client.