Twitter quietly tweaked its top tweet search results to display in order of relevance, rather than in reverse chronological order.
Senior software engineer, search quality Lisa Huang announced the change in a blog post, saying that users who were part of its test group engaged more with search results and spent more time on the social network.
She shared the image below, in which results of a search for #MrRobot are displayed chronologically on the left and by relevance on the right:

Huang explained the reasons for the change:
Twitter is live and real-time, so naturally, Twitter search must surface recent, yet still relevant, results. Historically, these search results have been largely presented in reverse chronological order. In many cases, however, the most recent results may not be what the searchers are looking for. They could be searching for popular tweets to engage with or to better understand context around the search query, and the most recent tweets are not necessarily best suited for that. In order to improve this experience, Twitter search shows relevance-ordered tweets at the top of your search results page. We retrieve tweet candidates from various sources within a larger time range and rank them with a machine-learned model. She also discussed some of the challenges Twitter faced:
The Twitter search results page has a blend of various result types: tweets, accounts, news, related searches, etc. We often encounter the problem where if we increase the quality...