Introduction

In some search applications, it may be necessary to immediately expose any changes made to the index to attain the best user experience. For example, such applications can be forums where a user may search for his/her newly edited post to confirm that the submission is successful and see how it ranked in the search results. If the application is database-backed, post-edit searches will always be able to bring back the submitted post as index updates, and searches are mostly real-time in a single database environment, assuming reads and writes are on the same table. However, performance can take a toll if changes are frequent and the search volume is high because frequent updates can cause high IO load, which in turn contributes to performance issues. Performing a lot of searches on a frequently updated table is not ideal as collisions between read and write requests are bound to happen and updates can block read requests. The read requests backlog can queue up to a point where...