L6
L6 — Staff Engineer (cross-team implications, capacity, migration)
At L6, the interviewer expects you to think about org-wide implications: which team owns what, capacity forecasting, migration paths, deprecation strategies, and cost per request.
Day-to-day responsibilities
- Design systems whose lifetime is measured in years, not sprints
- Set standards other teams will follow
- Propose migrations for legacy systems without breaking them
- Reason explicitly about cost, capacity, and headcount implications
Interview signals
- Sharding, replication, and multi-region reasoning done fluently
- Migration plan proposed for a hypothetical legacy system
- Capacity math done live (nodes, memory, cost per RPS)
- Discussion of ownership boundaries and team topology
Problem focus
- Global YouTube, Global Notification System, Ad Serving, Recommendation Infra
- Distributed databases, event streaming platforms, multi-region designs
Delivery advice
- Talk about the 3-year story of the system, not just launch day
- Show your cost model even if it's back-of-envelope
- When in doubt, propose a migration path — 'launch this alongside for 6 months'