Continue execution after sending response (Cloud Functions for Firebase)

You should expect that the HTTP function terminates the moment after you send the response. Any other behavior is some combination of luck or a race condition. Don't write code that depends on luck.

If you need to send a response to the client before the work is fully complete, you will need to kick off a second function to continue where the HTTP function left off. It's common to use a pub/sub function to do with. Have the HTTP function send a pub/sub message to another function, then terminate the HTTP function (by sending a response) only after the message is sent.

If the expected response is not pegged to the outcome of the execution, then you can use

module.exports.doSomeJob = functions.https.onRequest((req, res) => {
res.write('SUCCESS')
return doSomeAsyncJob()
.then(() => {
    emailSender.sendEmail();
})
.then(() => {
    res.end();
})
.catch(...);
});

This sends back a response a soon as a request is received, but keeps the function running until res.end() is called Your client can end the connection as soon as a response is received back, but the cloud function will keep running in the background Not sure if this helps, but it might be a workaround where the client needs a response within a very limited time, considering that executing pub/sub requires some extra processing on its own and takes time to execute