AJAX Crawling With Escaped Fragment URLs is a Deprecated Set up
Using AJAX crawling set up with escaped fragment URLs is a deprecated set up. At some point Google will be turning off support for escaped fragment URLs and will only crawl and render the hashbang URLs themselves.
AJAX Content Loaded After 20 Seconds Won’t Be Seen by Google
Content not loaded onto a page via AJAX immediately, probably won’t be seen by Google. John says 20-30 seconds is too long.
AJAX Loaded Hamburger Menus Won’t Be Seen by Google
Hamburger menus with content loaded via AJAX probably won’t be seen by Google.
Google is OK with Manipulated Back Buttons
Google doesn’t usually have a problem with Manipulating the back button behaviour, such as preventing users going back to Google’s search results.
AJAX is not 100% equivalent to normal static HTML pages, but it should be possible to make pages rank as well. Avoid using fragments in URLs, and check with Fetch and Render.
Escaped Fragment Support will be Dropped
Google’s support for the escaped fragment solution is going to continue in the mid-term.