Cheat sheets

A cheat sheet here is a page you write yourself and carry into the round, not a page to memorise. Each sheet gives the page to write by hand in the last ten minutes before the round, five moves in the order they are done, a drill you can run with a friend and a phone timer, and a rubric with one box per line to score a practice run. Times and counts come from the lesson named in each heading; where a number is the author's reading, the lesson says so.

C1. Recruiter call (lesson 4)

The page you write

Current: fixed ___  variable ___ (paid ___%)  PF ___  gratuity ___
Expected fixed: ___ to ___      Notice: ___ days, buyout ___
Level: ___    Why change: ______________________________
Pitch (under a minute, my resume's words): ______________________
Other processes: ____________    Office days: ____
Stock: granted ___  vested ___  to vest ___  next vest ___
Ask: levels, rounds and dates, who decides

Five moves

1. Answer the nine questions in the order asked: background, as a pitch under a minute; current CTC; expected; notice; relocation and office days; other processes; why change; level; process and timeline. At expected (3rd), ask the level (8th) yourself first.
2. State CTC by component, fixed first. Never round the variable up.
3. Give expected pay as a fixed number with a range, after you know the level.
4. Say your notice as your letter states it; mention a buyout only if the letter allows one.
5. Close by asking the process, the timeline and who decides.

Paper drill

Have a friend ask the nine questions and probes 10 and 11 in lesson 4's table, under a minute each, with a phone timer. Answer from the page, then repeat with the page face down while the friend pushes three times: a budget below your ask, a 30-day cut-off, a 30% cap on current pay. Score both runs; redo any line left empty.

Next stop: C2. Coding round (lesson 6), 2 min

C2. Coding round (lesson 6)

The page you write

My round is ___ minutes. Author's split of a 45-minute round, not a rule:
Clock: 0-4 clarify | 4-9 brute force + pattern + go-ahead
       9-29 code | 29-36 trace | 36-45 cost + follow-up
Nineteen patterns (lesson 6, "The pattern selector"): 1 two pointers,
2 fast and slow pointers, 3 list relinking, 4 sliding window, 5 prefix
sums and a map, 6 intervals and sweep line, 7 monotonic stack, 8 BFS and
DFS, 9 tree recursion, 10 topological sort, 11 union-find, 12 binary
search on the answer, 13 heap / top k / k-way merge, 14 backtracking,
15 DP, 16 Dijkstra, 17 trie, 18 recognise only: bits, Fenwick,
quickselect, 19 greedy. Also lesson 6: "Dynamic programming families"
and "Java details that cost marks".
n = 100,000: n squared = 10^10; n log n is about 1,660,964
Problem: ____________  Pattern: ____________  Brute force cost: ________
Edge cases: ______________________   Final time ____  space ____

Five moves

1. Clarify inputs, limits and examples in minutes 0 to 4, before touching code.
2. State the brute force and its cost, then name the pattern by minute 9.
3. Agree the plan out loud before you write.
4. Code from minute 9 to 29, then trace one example and two edge cases by hand.
5. State time and space, then take the follow-up; for each pattern the first one is "what if it does not fit, or arrives as a stream" (lesson 6, "Follow-ups after each solved problem").

Paper drill

Pick a problem from the lesson 6 list. Cover the solution, set a 45-minute timer and say every step aloud to a friend or an empty chair. Score with the rubric; repeat the weakest box in two days.

Next stop: C3. System design (lesson 8), 2 min

C3. System design (lesson 8)

The page you write

Clock: 0-5 clarify | 5-10 estimate | 10-15 API + data
       15-28 design | 28-40 deep dives | 40-45 wrap up
Seconds a day: 86,400    Peak factor: 3 (say it is yours)
Retries: 3 tries in each of 5 layers = 3^5 = 243; budget 10%
Quorum N,R,W = 3,2,2     Majority of five = 3
Writes/s ___ peak ___  Reads/s ___ peak ___  Storage a year ___ so ____
Per node (author's estimate, not measured): app server 1,000 real
requests/s; cache 50,000 ops/s; database 1,000 write transactions or
2,000 missed reads/s; log node 10,000 writes/s; hot row 500/s (16/s
with a 62 ms sync commit). Size at 1.5 x peak / budget.
Add-ons: lesson 8, "Recovery, SLOs and migrations: one table" and
"Overload: retry budgets, deadlines, shedding, breakers".
Behind? Cut API detail, fold the data model into labels,
shorten the estimate.

Five moves

1. Spend five minutes on clarifying scope and the one thing the system must do well.
2. Estimate load: writes and reads a second, peak at 3x, storage a year; end each with "so".
3. Sketch the API and the data model, then the main blocks.
4. Go deep on two failure or scale problems, with the mechanism named.
5. Wrap with the decisions you would defend, the main risk and what breaks first at ten times.

Paper drill

Blank page, phone timer, friend. Design a URL shortener (100 million links a month, 100 reads per write, 30-day month). Check against about 38.6 writes a second, 116 peak, 3,858 reads a second, 11,574 peak. Stop at each boundary.

Next stop: C4. Behavioural (lesson 10), 1 min

C4. Behavioural (lesson 10)

The page you write

Story = 120 seconds at most. Action beat = about 60 seconds (50%).
Author's plan.
Stories: S1 design ___ S2 incident ___ S3 lost ___ S4 won ___
         S5 led ___ S6 not built ___ S7 grew ___ S8 my fault ___
Beats: 0:00 situation | 0:15 task | 0:25 action (60 s) | 1:25 result
       1:45 reflection | stop at 2:00
Competencies: scope, ownership, conflict and disagreement, ambiguity, growth,
collaboration and leadership, judgement
Follow-up ladder: what did I do; what did others do; where is the
number from; what else did I consider; who disagreed; six months later;
what I would change; what if the other team said no

Five moves

1. Open with the headline and the stakes in the first two sentences.
2. Say "I" for the actions, and name the option you rejected and its cost.
3. Give one number against a baseline, and say how it was measured.
4. Close with what you changed afterwards.
5. Expect follow-ups such as "what exactly did you do?" and "how did you know?"; know both answers before you start.

Paper drill

Time each story with a phone and stop at 2:00. A friend asks the eight follow-up rungs in order; mark the rung where you said "we". Any story that fails two criteria goes back to the bank.

Sources