Waze keeps traffic flowing with 1M+ real-time reads per second on Memorystore

Editor’s note: Waze (a division of Google parent company Alphabet) depends on vast volumes of dynamic, real-time user session data to power its core navigation features, but scaling that data to support concurrent users worldwide required a new approach. Their team built a centralized Session Server backed by Memorystore for Redis Cluster, a fully managed service with 99.99% availability that supports partial updates and easily scales to Waze’s use case of over 1 million MGET commands per second with ~1ms latency. This architecture is the foundation for Waze’s continued backend modernization.

Real-time data drives the Waze app experience. Our turn-by-turn guidance, accident rerouting, and driver alerts depend on up-to-the-millisecond accuracy. But keeping that experience seamless for millions of concurrent sessions requires robust and battle hardened infrastructure that is built to manage a massive stream of user session data. This includes active navigation routes, user location, and driver reports that can appear and evolve within seconds.

Behind the scenes, user sessions are large, complex objects that update frequently and contribute to an extremely high volume of read and write operations. Session data was once locked in a monolithic service, tightly coupled to a single backend instance. That made it hard to scale and blocked other microservices from accessing the real-time session state. To modernize, we needed a shared, low-latency solution that could handle these sessions in real time and at global scale. Memorystore for Redis Cluster made that possible.

Choosing the right route

As we planned the move to a microservices-based backend, we evaluated our options, including Redis Enterprise Cloud, a self-managed Redis cluster, or continuing with our existing Memcached via Memorystore deployment. In the legacy setup, Memcached stored session data behind the monolithic Realtime (RT) server, but it lacked the replication, advanced data types, and partial update capabilities we wanted. We knew Redis had the right capabilities, but managing it ourselves or through a third-party provider would add operational overhead. 

Memorystore for Redis Cluster offered the best of both worlds. It’s a fully managed service from Google Cloud with the performance, scalability, and resilience to meet Waze’s real-time demands. It delivers a 99.99% SLA and a clustered architecture for horizontal scaling. With the database decision made, we planned a careful migration from Memcached to Memorystore for Redis using a dual-write approach. For a period, both systems were updated in parallel until data parity was confirmed. Then we cut over to Redis with zero downtime.

Waze’s new data engine

From there, we built a centralized Session Server – our new command center for active user sessions – as a wrapper around Memorystore for Redis Cluster. This service became the single source of truth for all active user sessions, replacing the tight coupling between session data and the monolithic RT server. The Session Server exposes simple gRPC APIs, allowing any backend microservice to read from or write to the session state directly, including RT during the migration. This eliminated the need for client affinity, freed us from routing all session traffic through a single service, and made session data accessible across the platform.

We designed the system for resilience and scale from the ground up. Redis clustering and sharding remove single points of contention, letting us scale horizontally as demand grows. Built-in replication and automatic failover are designed to keep sessions online. While node replacements may briefly increase failure rates and latency for a short period, sessions are designed to stay online, allowing the navigation experience to quickly stabilize. And with support for direct gRPC calls from the mobile client to any backend service, we can use more flexible design patterns while shaving precious milliseconds off the real-time path.

Fewer pit stops, faster rides

Moving from Memcached’s 99.9% SLA to Memorystore for Redis Cluster’s 99.99% means higher availability and resiliency from the service. Load testing proved the new architecture can sustain full production traffic, comfortably handling bursts of up to 1 million MGET commands per second with a stable sub-millisecond service latency. 

Because Memorystore for Redis supports partial updates, we can change individual fields within a session object rather than rewriting the entire record. That reduces network traffic, speeds up write performance, and makes the system more efficient overall – especially important when sessions can grow to many megabytes in size. These efficiencies translate directly into giving our engineering teams more time to focus on application-level performance and new feature development.

Session data in Memorystore for Redis Cluster is now integral to Waze’s core features, from evaluating configurations to triggering real-time updates for drivers. It supports today’s demands and is built to handle what’s ahead.

The road ahead

By proving Memorystore for Redis Cluster in one of Waze’s most critical paths, we’ve built the confidence to use it in other high-throughput caching scenarios across the platform. The centralized Session Server and clustered Redis architecture are now standard building blocks in our backend, which we can apply to new services without starting from scratch.

With that initial critical path complete, our next major focus is the migration of all remaining legacy session management from our RT server. This work will ultimately give every microservice independent access to update session data. Looking ahead, we're also focused on scaling Memorystore for Redis Cluster to meet future user growth and fine-tuning it for both cost and performance.

Learn more

Waze’s story showcases the power and flexibility of Memorystore for Redis Cluster, a fully managed service with 99.99% availability for high-scale, real-time workloads. 

• Learn more about the power of Memorystore and get started for free. 

• See Memorystore for Redis Cluster product documentation.