MLSD-026 · DESIGN PRACTICE
Practice: Feature platform
Draft the complete decision system before revealing the guidance. Use a 45-minute rehearsal budget and adapt it to the interviewer’s direction.
Preserve eligibility, available-at-decision inputs, mature labels, bounded work and compatible releases. Explain alternatives and test a normal, boundary and failure case.
Your practice draft
Design a shared feature platform for 5,000 reads/s and 20 features/request. Specify the SQL/cache baseline, temporal and version contracts, APIs, schema, backfill checkpointing, parity goldens, deletion fencing and rollout. Work F1/F2 at each boundary and recover after a lost chunk acknowledgement.
Saved locally on this device. The worked answer does not score your draft. Existing lesson notes and completion are separate.
Progressive hints
Hint 1
Start with tenant/entity/version/epoch, event time versus actual activation and a declared freshness/default contract.
Hint 2
Pin input/transform/target versions; distinguish raw ingestion ACK, successful activation and committed chunk effects.
Hint 3
Use exact semantic parity before numeric tolerance; a compatible rollback cannot bypass current permission.
Self-review evidence
For each criterion, record Missing, Prompted, Independent or Adaptive reasoning. No automated scoring or offer prediction is provided.
- Engineer: coherent baseline, complete semantic definition, precise API/status and temporal boundary math.
- Senior: conditional projection, bounded idempotent backfill, independent parity tests, schema/index/atomicity and failure recovery.
- Staff: ownership, tenant resource/access boundaries, migration/retention/rollback constraints and cost evidence.
- All levels: distinguish executed fixtures from production guarantees, independent review and consumer quality.
Reveal worked design guidance
F1 is selected at 10:00; F2 at 10:10/10:15/10:30; 10:45 is stale/default. Scores are 3 for F1 and 9 for F2 under /10; wrong /100 is rejected despite producing a finite 1.8. C1 [0,2) advances once to cursor 2/version 2 and identical retry is unchanged. Current generation fences reads and publication, including historical exports; deleted/denied has no score. The complete design adds owned contracts, valid schema relationships, bounded resource work and compatible rollout rather than claiming a toy fixture is a running service.
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