Senior Software Engineer, Storage Cache at Roblox — building a multitenant ValKey caching platform at billion-user scale

Roblox's Cache team (Infra Storage org) is rebuilding its caching layer on ValKey for sub-millisecond latency and 90% cost reduction at up to 1B DAU scale. This interview goes deep on distributed caching internals — multitenancy isolation, hot-key mitigation, chaos testing, and Go/C++ systems experience — well beyond generic backend-engineer questions.

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What this interview tests

Multitenant caching architecture: data/resource/failure isolation on ValKey
Hot-key mitigation, head-of-line blocking, CPU/memory utilization at scale
Distributed systems fundamentals: gossip protocol limits, partial failure handling
Go and C++ hands-on systems programming depth
Active/Active on Kubernetes/Nomad; chaos testing for 99.99%+ availability
Bonus depth: Redis/ValKey internals, custom modules, jemalloc, caching proxies

Common question themes

How would you design tenant isolation (data, resource, failure) in a shared caching service

Walk me through how you'd diagnose and fix hot-key contention or head-of-line blocking in production

Describe the hardest distributed-systems bottleneck you've resolved at scale — gossip protocol or partial-failure related

How do you design chaos/fault-injection testing to validate 99.99%+ availability

What's your experience running Active/Active systems on Kubernetes or Nomad

Have you contributed to or extended Redis/ValKey internals — custom modules, Lua scripting, memory allocator tuning

How do you mentor engineers and drive design reviews / architectural standards on a team

How candidates describe it

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