How can I receive "immediately" notification about new questions posted that meet certain search criteria?

Question

I noticed that you can do any tag combination with or and and (just separate the tags for space) operators in the search box and when you hit the search button you will be redirected to an URL like this one:

https://stackoverflow.com/questions/tagged/python+or+python-2.7

This URL corresponds to the search: [python] or [python-2.7]

While you are on a page with an URL that starts with https://stackoverflow.com/questions/tagged/ (like the above example) you receive updates about new questions with messages like: "4 questions with new activity". If you click those messages, the new questions just show up on top of the questions list. The appearance of those messages in such URLs are "immediately" after the questions are posted, as well as the modification of the page title indicating new questions are available.

On the other hand, if you specify a search like [python] title:python in the search box and hit Enter you will be redirected to a page with URL like this one:

https://stackoverflow.com/search?q=%5Bpython%5D+title%3Apython

This URL corresponds to the search: [python] title:python

While you are on a page with an URL that starts with https://stackoverflow.com/search (like the above example) you will not receive messages notifying you about new questions that meet the search criteria, nor does the page title get updated. Even when you refresh the page (executing the search again) new questions show up seconds after they are already available on the first kind of URL (https://stackoverflow.com/questions/tagged/).

So my questions are:

1. Does there exist a way to construct a custom query with more than tags and search criteria, whose results page gets updated automatically and as fast as the first kind of URL I mentioned? If someone know about how to do this on Stack Exchange or outside using any web application (no mobile) that will be great.

2. Does somebody know if there exists an API call to Stack Exchange that leaves the connection to do some kind of stream in a way that new posts get detected immediately?

3. What would be the best way to receive immediately the new questions that meet certain criteria using the Stack Exchange API?

Answer 1

If you take a look at the https://Stackexchange.com/filters you can see how to create a filter that you can subscribe to via RSS or email. Email updates are limited to a frequency of 15 minutes or longer. I've set up a filter you can check out using the python tags that you specified above.

We are currently working on improvements to this feature. This includes better discoverability via integration into the Q&A sites. This is still a work in progress. It would be great to know why you want immediate updates. For many tags that can create quite the flood of email if you subscribe that way.

Answer 2

There's an RSS feed for each tag. You'll still have to set up a RSS client locally to alert you in a suitable fashion.

RSS feed of your favorite tags explains this in some more detail although the site has been revamped since the answers there were written, and many of the RSS decorations seem to be gone. The underlying feature still exists, though (but removing the icons which make it discoverable could be a signal that it is going to be removed one day?)

For example, https://stackoverflow.com/feeds/tag/python+or+python2.7

As for your API question, I believe you should be able to construct a filter which selects only a few tags, but I don't have first-hand experience with that. Try https://api.stackexchange.com/docs/search#order=desc&sort=activity&tagged=python&filter=default&site=stackoverflow&run=true (maybe you need one per tag).