Week 8 · Sat Sep 19, 2026 · Sep 14-20, 2026

Day 6: Two 45-minute Adaptive Mocks

Independent adaptive mocks for Web Crawler and Job Scheduler, plus a transfer pressure drill for Price Tracking.

Can you produce Staff mechanisms under clock pressure without reading?Frontier · leases · retries · dedupe · recovery3 Heap/Priority Queue slots

Exact Time Blocks

Follow the Week 4 delivery pattern: blank-page first, source reading second, DDIA decision third, spoken close, contiguous algorithm practice, evening recall.

TimeBlockRequired output
08:30Wake + setupOpen this page, start the board, write the day question: Can you produce Staff mechanisms under clock pressure without reading?
08:50—09:00Board setList entities, queues, leases, retry states, dedupe keys, metrics before reading.
09:00—10:05Blank-page attempt + Hello readingRun Web Crawler 45 minutes, then Job Scheduler 45 minutes. The moderator only injects failures that follow your own design choices. Capture the first missing invariant, not a long transcript.
10:05—10:45Deep dive + DDIA decisionAfter both mocks, repair exactly two dives: one crawler dive and one scheduler dive. Each repair must include invariant, failure, recovery, and metric.
10:45—10:55Spoken closeRecord the new default answer for politeness and for exactly-once illusion in the scorecard.
14:30—16:15NeetCode Heap/Priority QueueComplete contiguous slots W8-H16—W8-H18; capture invariant and bug risk for each.
20:30—21:15Recall / Q&A / mockUse Staff Q&A, lecture assets, or mock script for the day's system.

Canonical Heading Anchors

Read only the listed Hello Interview headings for today's assignment. Every link is a direct day-page anchor.

What is Expected at Each Level?Day 6
  • Mock rubric calibration
Mid-levelDay 6
  • Rubric contrast
SeniorDay 6
  • Senior+ bar
Staff+Day 6
  • Staff bar
What is Expected at Each Level?Day 6
  • Mock rubric calibration
Mid-levelDay 6
  • Rubric contrast
SeniorDay 6
  • Senior+ bar
Staff+Day 6
  • Staff bar
What is Expected at Each Level?Day 6
  • Transfer rubric calibration
Mid-levelDay 6
  • Rubric contrast
SeniorDay 6
  • Senior+ bar
Staff+Day 6
  • Staff transfer bar

Decision Notes

  • CORE means you must answer requirement, HLD, deep dive, failure, recovery, metric, and Staff-level tradeoff.
  • TRANSFER means blind attempt first, then delta against source, invalid assumption, new bottleneck, and follow-up pressure question.
  • Do not add open-ended AI radar unless it changes a concrete Week 8 design decision; this week it does not.

DDIA Decision Map

Use exact sections only from Ch5, Ch9, and Ch12.

ChapterExact DDIA decision sectionConcrete Week 8 use
Ch9故障注入Mock injects worker pause, queue redelivery, and stale lease completion.
Ch12容错Score whether replay and rebuild stories are explicit.
Ch12幂等性Score whether each retry path has an idempotency key or conditional write.

Heap/Priority Queue Slots

Three contiguous slots today. Keep one invariant and one failure mode per problem.

SlotProblemPatternInvariant / bug riskTime · Space
W8-H16 Network Delay Time Dijkstra The heap priority is best-known arrival time, not edge weight. O(E log V) · O(V+E)
W8-H17 Swim in Rising Water best-first search Path cost is the maximum cell height seen so far. O(n^2 log n) · O(n^2)
W8-H18 Path With Minimum Effort Dijkstra on max edge Relax by max(current effort, next edge effort). O(mn log mn) · O(mn)

Evidence To Save

One compact artifact is enough if it proves mechanism depth.

Invariant

State safety

Name the state that survives restart and the write that makes retry safe.

Failure

Concrete break

Use a worker crash, zombie lease, redelivery, poison message, stale robots decision, or duplicate price event.

Metric

Operational proof

Attach lag, retry rate, duplicate suppression, stale lease reject count, host politeness violation, or alert freshness.

Local study materials
Detailed lecture notes, audio, recall scripts, PDFs, Staff Q&A, and mock packs are archived locally and are intentionally not published on this site.