Interviewing next week
A short route for engineers who already know the concepts: four stops, about an hour each, so most of the week is left for practice. It covers gaps that commonly cost people the round.
For: Mid-senior engineers 7–14 days before a round
After this path
Walk into the round with two of the most common system shapes, the failure-mode framework and your consistency choices rehearsed.
- 1Pattern
Read-heavy
Use caches, replicas and edge layers to absorb repeated reads before they reach the primary database.
Why this, here: Re-read the scaling path (v1 → v2 → v3) until you can narrate it on a whiteboard cold.
- 2Pattern
Fan-out: on write vs on read
Choose whether distribution happens on write, on read, or with a measured hybrid boundary.
Why this, here: The Twitter / feed question in distilled form. At scale the answer is often a hybrid, and the threshold is the point.
Checkpoint
Halfway check: given a prompt for an Instagram-scale feed, would you choose push, pull, or hybrid — and what tips the decision? If your answer is just “hybrid”, you don’t have the threshold yet.
- 3Skill
Failure mode analysis
What fails, blast radius, graceful degradation, retries, circuit breakers.
Why this, here: Your design will be pressure-tested on "what fails". Have the per-component breakdown ready.
Checkpoint
Rehearse aloud: for a read-heavy system with cache + DB + replica, name one failure mode per component and one mitigation. Time yourself — staff rounds want this in under a minute.
- 4Skill
Consistency trade-offs
Strong vs eventual vs causal, quorum, read-your-writes.
Why this, here: Choose consistency per data class, not per system. Candidates often fumble this.