Case Study: Reddit achieves fast, scalable, and highly reliable search with Lucidworks Fusion

How the team at Reddit destroys global productivity with cat photos and Lucidworks Fusion

Reddit — the “front page of the internet” with 330+ million monthly users, ~10 million posts per month and millions of daily comments — needed a search system that could scale, stay fast, and return relevant results. After cycling through five different search stacks over 12 years, search was consuming disproportionate resources, suffering increasing latency and timeouts, and could not keep up with Reddit’s growth.

Reddit partnered with Lucidworks to build search on Fusion (which includes Apache Solr), splitting the app into a microservice, a nightly and streaming ingest pipeline, and a Fusion cluster. The new deployment reduced the cluster footprint from roughly 200 nodes to the mid‑20s, cut full-corpus index time from two weeks to two days, raised update throughput to thousands per second and now serves hundreds of queries per second with improved uptime — all while maintaining or improving result relevance for Reddit’s 330M+ users.

Reddit

Nick Caldwell

Vice President of Engineering