Day 2 · Tue 2026-10-06 · LeetCode FULL
LeetCode Staff depth: sandbox isolation, budgets, queues, tests, and contest scale
Week 11 trains two designs with one operating spine: admission, isolation, durable work, queue/backpressure, streaming/reconnect, derived state, evals, and recovery.
3contiguous 1-D DP slots
25-35mattempt + follow-up window
Staffinvariant, failure, recovery, metrics
Exact Daily Schedule
No drift: the same six blocks run every day.
| Time | Block | Contract |
|---|---|---|
| 08:50-09:00 | Target | Write one Staff-level invariant and one failure window before reading. |
| 09:00-10:05 | Project design | 25-35m LeetCode follow-up attempt, then isolation and contest deep dives. |
| 10:05-10:45 | DDIA / source grounding | Map the design to exact DDIA anchors and only direct applied-AI sources. |
| 10:45-10:55 | Spoken close | Record the architecture in English, then say the Chinese invariant aloud. |
| 14:30-16:15 | 1-D DP contiguous block | Three NeetCode slots below; each slot is 25-35 minutes plus follow-up. |
| 20:30-21:15 | Recall / artifact | Run English Senior+/Staff recall and patch the scorecard evidence. |
Canonical Hello Interview Anchors
Direct day-page anchors only. Source titles were verified live before build.
| Canonical anchor | Disposition | Design decision |
|---|---|---|
| Potential Deep Dives | FULL deep dive | Lead follow-ups from risk, not from component inventory. |
| How will the system support isolation and security when running user code? | FULL deep dive | Sandbox, cgroup, seccomp, filesystem, network, and deadline budgets are the design center. |
| How would you make fetching the leaderboard more efficient? | FULL deep dive | Maintain a scored, versioned top-K projection; recompute on dispute. |
| How would the system scale to support competitions with 100,000 users? | FULL deep dive | Shard contest queues and protect runner pools with admission control. |
| How would the system handle running test cases? | FULL deep dive | Treat each test batch as an attempt with deterministic inputs and bounded outputs. |
| Final Design | FULL synthesis | Close with a dataflow that preserves state after retries and crashes. |
| What is Expected at Each Level | FULL bar | Convert level expectations into answer depth. |
| Mid-Level | FULL bar | Mid-level must produce a coherent baseline. |
| Senior | FULL bar | Senior owns isolation, queues, and scale trade-offs. |
| Staff | FULL bar | Staff anticipates adversarial code, uncertain execution, and operational recovery. |
Exact DDIA Mapping
Only Ch5, Ch9, and Ch13 sections are in scope.
| Chapter | Exact section | Interview use |
|---|---|---|
| Ch9 | 故障与部分失效 | A running attempt may have succeeded, failed, or become unknowable until state is committed. |
| Ch9 | 超时和无界延迟 | Backpressure, deadlines, and admission are product behavior, not hidden implementation details. |
| Ch9 | 隔离僵尸进程和延迟请求 | Runner result writes carry lease or fencing tokens to reject old workers. |
Applied AI Source Gate
First-party/original sources appear only when they change a serving, eval, security, or operating decision.
No applied-AI source is introduced today unless it changes a concrete serving, eval, security, or operating decision.
21-Slot 1-D DP Runway
Today is slot 4-6 of 21, contiguous across the week.
| Block | NeetCode problem | Mode | Invariant | 25-35m follow-up | Complexity |
|---|---|---|---|---|---|
| 14:30-15:05 | House Robber II | Circular split | Solve two linear ranges because first and last cannot both be chosen. | Ask for n=1 and n=2 edge cases. | O(n) / O(1) |
| 15:05-15:40 | Longest Palindromic Substring | Center expansion | Each answer expands around one or two centers; keep best interval. | Ask when DP table is preferable. | O(n^2) / O(1) |
| 15:40-16:15 | Palindromic Substrings | Count centers | Every center expansion contributes one substring per successful radius. | Ask how to avoid duplicate counting. | O(n^2) / O(1) |
Artifacts And Recall
Use these in the evening block and scorecard.
Required spoken close: explain one invariant, one failure window, one recovery path, and one metric in English. Then restate the same design decision in Chinese without adding new components.
Detailed lecture notes, audio, recall scripts, PDFs, Staff Q&A, and mock packs are archived locally and are intentionally not published on this site.