Zero downtime Upgrade: Yelp’s Cassandra 4.x Upgrade Story Mark Surnin and Muhammad Junaid Muzammil, Software Engineer Apr 7, 2026 The Database Reliability Engineering team at Yelp seamlessly upgraded more than...

Yelp's platform is a central hub for consumers and businesses, offering insights into local businesses, user reviews, and recommendations. Through articles, guides, and user-generated content, Yelp offers insights into discovering restaurants, shops, and services in various locations. Readers can learn about reading and writing reviews, finding popular businesses, and exploring local communities to make informed decisions about where to eat, shop, or visit.

Yelp Engineering

Yelp's Database Reliability Engineering team upgraded over a thousand Cassandra nodes from version 3.11 to 4.1 with zero downtime. The post covers their upgrade strategy including benchmarking (4% p99 latency improvement, 11% throughput gain, up to 58% p99 reduction on key clusters), compatibility challenges with Stargate proxy and Cassandra Source Connector, and a three-stage automated upgrade process (pre-flight, flight, post-flight). Key lessons include a Stargate 2.x regression causing slower range queries (resolved by downgrading to 1.x), schema disagreement on CDC-enabled clusters, and the value of running version-specific components in parallel during the transition. The upgrade was performed in-place via rolling restart on Kubernetes, avoiding the cost and complexity of a separate DC approach.

Zero downtime Upgrade: Yelp’s Cassandra 4.x Upgrade Story

<p>This is a good reminder that distributed systems don’t fail because upgrades are hard—they fail because assumptions aren’t tested in partial-upgrade states.</p>
