Low latency and redundant proof of possession for content subscription with outbound message synchronization

A system for content subscription, the system comprising a user device and a server, user device being configured to communicate with the server, the server being implemented on one or more computers, wherein:

• the user device has a first network endpoint and is configured with a web browser, wherein the web browser is configured with popup instructions operable to cause the web browser to perform popup operations comprising:
• generating a popup from a parent web page, the popup including (i) a call to action to subscribe to content at the first network endpoint and (ii) an end-point input field, wherein the content has an identifier (content ID) and includes SMS messages;
• in response to user input indicating acceptance of the call to action, calling a service on the server for content subscription and proof of endpoint possession, wherein one indication of acceptance is receipt of user input specifying the first network endpoint, and wherein the call to the service specifies the first network endpoint;
• obtaining a one-time passcode received at the first network endpoint on the user device and sending the passcode to the service;
• in response to receiving from the service an indication of successful proof of endpoint possession, deep linking to a messaging application and pre-populating a message addressed to a second network endpoint from which subscribed content is sent;
• and
• sending one or more HTML parameters extracted from the parent web page to the service, wherein the one or more HTML parameters indicate a traffic source of the parent web page;
• and
• the server is configured to implement the service and perform service operations comprising:
• in response to the call from the web browser for content subscription and proof of possession, generating a one-time passcode and sending the passcode to the first network endpoint from a third network endpoint that is different from the second network endpoint;
• in response to receiving a one-time passcode from the web browser, comparing the received one-time passcode with the generated one-time passcode and, if they match, creating and storing a subscription record that includes the first network endpoint and returning to the browser an indication that proof of possession has been completed;
• and
• appending the record with the one or more HTML parameters.