For some reason, a day before Google Reader was closed, Google Developers blog published an article about PubSubHubbbub, feeds and the Google Feeds API. PubSubHubbub (PuSH) is a protocol for sending notifications when a feed is updated. “Using the PuSH protocol, servers can subscribe to an almost arbitrarily large number of feeds and receive updates as they occur.” Google encourages publishers to submit their feeds to a public PuSH hub like Google’s hub and Superfeedr’s Open PubSubHubbub Hub.
The most interesting part of the post is this one: “Google directly hosts many feed producers (e.g. Blogger is one of the largest feed sources on the web) and is a feed consumer too (e.g. many webmasters use feeds to tell our Search system about changes on their sites). Our PuSH hub offers easy access to hundreds of millions of Google-hosted feeds, as well as hundreds of millions of other feeds available via the PuSH ecosystem and through active polling.” And something else: “We are planning some improvements to the Feed API, as part of our ongoing infrastructure work.”
This means that Google’s feed processing backend will continue to exist, but will focus on the Google Feeds API and Google Search index updates. Google Feeds API will also continue to exist and third-party feed readers could use it. All of this was an important part of the Google Reader backend, but Google Reader also had to manage subscriptions, labels, the read/unread state, create a search index for each user.