System Design — Rack Management at Fleet Scale
The design walkthroughs for this role. Each takes a single-rack capability (built in the phases) and scales it to a fleet, with the requirements-gathering, architecture, hard decisions/tradeoffs, failure modes, and operations an interviewer probes.
| Walkthrough | Prompt | Phases |
|---|---|---|
| 01 — Rack Management Control Plane | "Design the software that manages a fleet of AI racks." | 01, 03, 06, 13 |
| 02 — Unified Telemetry Pipeline | "Design fleet-wide telemetry for heterogeneous rack hardware." | 03, 07 |
| 03 — Fleet Firmware Update System | "Update firmware across 10,000 nodes without bricking the fleet." | 08, 06, 11 |
| 04 — Multi-Tenant Isolation & Secure Boot | "Design isolation/trust for a multi-tenant sovereign rack." | 09, 06 |
| 05 — Bare-Metal Provisioning Service | "Design a service to onboard racks from bare metal." | 05, 01, 12 |
How to run a system-design round
- Drive the requirements first — scale (how many racks/sites?), tenancy, workload mix, hardware heterogeneity, sovereignty/air-gap, SLOs. Don't design before you've scoped.
- Start from the single-rack design (the phases/capstone) and state explicitly what changes at scale — that's the value-add and what separates Senior/Staff.
- Name the hard decisions and the tradeoffs (the part interviewers grade): the driver abstraction, push vs poll, canary vs blue/green, soft vs hard tenancy, central vs proxy.
- Cover failure modes & operations — a flaky BMC, a bad firmware, a correlated PDU failure, a control-plane restart, fleet upgrades — with the reliability patterns (Phase 10) and observability (Phase 07).
- Be honest about limits — what you'd defer, what you'd measure, where you're uncertain. (Phase 12 communication.)
The recurring spine across all five: one data model, one reconcile loop, clean seams (the driver abstraction), and rollouts that are gated/canaried/reversible/failure-domain-aware.