Week 06 (Jun 29 – Jul 5, 2026) — BACKTRACKING (Sprint S2 of 8)
Sprint goal: DSA + HLD/SD + Redis done by Aug 15. This week: Backtracking (9). Timer on, solo, no peek till timer expires.
→ Curriculum: [[Coach/project_dsa_sd_curriculum]] | Coach state: [[synthesis/Coach Hub]]
Goals This Week
DSA Problem Set (9)
| # | Problem | LC | Diff | Target | Solved? | Time | Bugs / notes |
|---|
| 1 | Subsets | 78 | M | 20 min | ☐ | | template: choose/explore/un-choose |
| 2 | Combination Sum | 39 | M | 25 min | ☐ | | reuse allowed → don't advance idx |
| 3 | Permutations | 46 | M | 25 min | ☐ | | used[] vs swap |
| 4 | Subsets II | 90 | M | 25 min | ☐ | | sort + skip dup at same level |
| 5 | Combination Sum II | 40 | M | 30 min | ☐ | | dup skip + advance idx |
| 6 | Word Search | 79 | M | 30 min | ☐ | | grid DFS + visited mark/unmark |
| 7 | Palindrome Partitioning | 131 | M | 30 min | ☐ | | isPalindrome helper + cut points |
| 8 | Letter Combinations of Phone No. | 17 | M | 20 min | ☐ | | digit→letters map |
| 9 | N-Queens | 51 | H | 40 min | ☐ | | col/diag/anti-diag sets |
Score: __/9 on time
SD + Redis + DDIA
| Item | Status | Notes |
|---|
| SD: Rate Limiter | ✅ Done 2026-07-02 | Full note: 5 algos, Redis INCR+EXPIRE, Lyft rules, headers, distributed race (Lua/sorted-set) + sync (centralized store), L7 vs L3. → [[Rate Limiter]] |
| SD: Design Key-Value Store | 🔵 this week | Requirements, single-node (hash index, WAL, LSM/SSTable), replication (quorum N/W/R), partitioning, conflict resolution (vector clocks), read-repair, hinted handoff. DDIA Ch5–6 territory. |
| SD: Consistent Hashing | 🔵 this week | Ring, hash space, virtual nodes, add/remove node → minimal key movement, why modulo-N fails. → existing [[Consistent Hashing]] page for reference. |
| Redis: TTL + token-bucket | ⬜ | EXPIRE, INCR, atomic counter; token-bucket via Lua |
| DDIA: Ch6 Replication | ⬜ | leader-follower, multi-leader, leaderless, quorum, read-repair (pairs w/ KV store) |
Daily Plan (compact)
- Mon: theory block (backtracking template) + LC 78
- Tue: LC 39, 46
- Wed: LC 90, 40 + Redis TTL video
- Thu: LC 79, 17 + SD Rate Limiter high-level
- Fri: LC 131 + SD Rate Limiter deep + DDIA Ch6.2
- Sat: LC 51 (hard) + Rate Limiter whiteboard cold
- Sun: retro + scorecard + create S3 tracker
Decision Gate (Sun Jul 5)
| Score | Verdict | S3 |
|---|
| 7–9 | Pass strong | Graphs (13) + Twitter Feed + Redis sorted sets |
| 5–6 | Patchy | Graphs + retry weakest backtracking |
| <5 | Fail | Repeat Backtracking in S3 |
Hours Log
| Day | Planned | Actual |
|---|
| Mon–Sun | ~24h | |
Retro (fill Sun)
- Solved on time: __/9 | Weakest: __ | SD: __ | Redis: __ | DDIA: __ | S3 decision: __