WEEK 09 · 2026.09.21-09.27 · WRITER GATE
Day 7 - Week 9 repair, synthesis and READY_FOR_REVIEW
2026-09-27 · SUN · 不读新系统。只修复 Week 9 material error 一次，完成 scorecard、mock evidence、media/link/visual evidence and production record。
今日固定时间表
三个学习窗口必须保持 exactly 08:50-10:55, 14:30-16:15, 20:30-21:15。
| 08:50-09:20 | 08:50-10:55 system design Reattempt weakest system: choose one FB/News/Yelp prompt and answer from blank page. |
|---|---|
| 09:20-10:05 | 08:50-10:55 system design Synthesis matrix: source of truth, derived index, recall, rank, presentation and freshness guard per project. |
| 10:05-10:35 | 08:50-10:55 system design Scorecard and artifact contract: confirm FULL/TRANSFER outputs and no PDFs. |
| 10:35-10:55 | 08:50-10:55 system design Writer gate: run one deterministic/link/visual check and write READY_FOR_REVIEW. |
| 14:30-16:15 | NeetCode Graphs Three contiguous Graphs slots below; no other tag. |
| 20:30-21:15 | 20:30-21:15: final English recall, transfer deltas and scorecard sign-off. |
算法模块
NeetCode Graphs, exactly three slots today, contiguous slots 19-21 of 21.
| # | Problem / mode | Pattern | Invariant | Bug risk | Time | Space |
|---|---|---|---|---|---|---|
| 19 | Number of Islands Timed Graphs · NEW · 30m solve + 5m evidence | timed component count | visited marking is the source of truth | stack overflow or revisiting cells | O(mn) | O(mn) |
| 20 | Course Schedule Timed Graphs · NEW · 30m solve + 5m evidence | timed topo/cycle proof | every edge is considered once under tri-color state | returning true on a currently visiting node | O(V+E) | O(V+E) |
| 21 | Rotting Oranges Timed Graphs · NEW · 30m solve + 5m evidence | timed multi-source BFS | layer count equals elapsed minutes after initial frontier | off-by-one minute when initial state already solved | O(mn) | O(mn) |
今日产出
| 必须交付 | Week 9 production evidence; no Week 10 preview. |
|---|---|
| 修复规则 | Repair material errors once; avoid repeated visual passes and open-ended research. |
Week 9 Inventory Closure
今天不读新材料，只关闭所有已映射 live headings。
| Project | Live headings | Disposition |
|---|---|---|
| FB Post Search | 41 | FULL complete across Day 1-2 |
| News Aggregator / Google News | 20 | TRANSFER complete across Day 3-4 |
| Yelp | 21 | TRANSFER complete across Day 5-6 |
DDIA 精确决策卡
Only DDIA Ch4 and Ch13 decision links are allowed.
| Day | Project | Decision | Link |
|---|---|---|---|
| Day 1 | FB Post Search | keyword search is an inverted index, not SQL LIKE | https://ddia.vonng.com/ch4/#sec_storage_full_text |
| Day 1 | FB Post Search | recency and like sort need index/ranker fields, not presentation sorting | https://ddia.vonng.com/ch4/#sec_storage_index_multicolumn |
| Day 2 | FB Post Search | large write volume chooses update pipeline and refresh interval consciously | https://ddia.vonng.com/ch4/#sec_storage_btree_lsm_comparison |
| Day 2 | FB Post Search | rebuild/search index as derived state, then swap safely | https://ddia.vonng.com/ch13/#id340 |
| Day 3 | News Aggregator | feed rows and index documents are derived from crawled source articles | https://ddia.vonng.com/ch13/#id446 |
| Day 3 | News Aggregator | homepage/category feed caches are materialized views with staleness budgets | https://ddia.vonng.com/ch13/#id451 |
| Day 4 | News Aggregator | freshness SLO requires observing index lag and stale derived state | https://ddia.vonng.com/ch13/#sec_future_observing |
| Day 4 | News Aggregator | schema/ranking evolution needs reprocessing rather than hand edits | https://ddia.vonng.com/ch13/#sec_future_reprocessing |
| Day 5 | Yelp | geo search uses multidimensional indexes or grid cells, not naked lat/lng scans | https://ddia.vonng.com/ch4/#sec_storage_multidimensional |
| Day 5 | Yelp | category + price + open_now + distance are composite filter/rank constraints | https://ddia.vonng.com/ch4/#sec_storage_index_multicolumn |
| Day 6 | Yelp | text plus geo search combines full text retrieval with precise second-pass filters | https://ddia.vonng.com/ch4/#sec_storage_full_text |
| Day 6 | Yelp | review/rating aggregate and search index are derived state that needs verification | https://ddia.vonng.com/ch13/#sec_future_verification |
Artifacts
PDF is intentionally absent; Week 9 requires MP3 only for the FULL/TRANSFER scripts.
Detailed lecture notes, audio, recall scripts, PDFs, Staff Q&A, and mock packs are archived locally and are intentionally not published on this site.