Stack Overflow currently uses Redis for its distributed cache, buffering high-volume operations, work queues, message distribution, and storing transient data across multiple local and geo-distributed replicas for redundancy. The document discusses Stack Overflow's plans to upgrade its Redis infrastructure including migrating to newer Redis versions for new features, upgrading applications and libraries to .NET Core, and improving high availability through Redis clustering. The future opportunities that Redis upgrades provide for both Stack Overflow and its library consumers are also noted.

1. Stack Overflow’s
next steps in Redis
Marc Gravell, Stack Overflow
@marcgravell

2. Current Usage
How does Stack Overflow use Redis today?
• High performance distributed cache
• Buffer for high-volume operations
• Work queues for deferred operations
• Message distribution
• High perf transient data
• Local and geo-distributed replicas for redundancy.

3. Topology
NY, 01 NY, 02
CO, 01 CO, 02
classic redis-server v4.0.2
multiple service instances per box
multiple databases per instance
CentOS 7

4. Topology

5. So… where do we want to go?
• step zero: get onto redis vCurrent (5, 6, …)
• migrate “enterprise” to linux
migrate apps and libraries to .NET Core
get SQL Server working
upgrade Redis o/
• lots of work, but lots of side benefits (not just redis!).

6. So… where do we want to go?
• v3 cluster
redundancy
maintenance
distributed keyspace

7. So… where do we want to go?
• v4
modules
• RediSearch?
• v5
streams
consumer groups
• v6
key frequency metadata
client library updates
RESP3

8. Summary
• We have lots to do
to catch up to today
and to keep up with the day after that
• New features to exploit
for ourselves
and for our library consumers
But: the future looks positive!

9. Thank you!