Training modules
Architect distributed systems at FAANG scale. Cover load balancing, sharding, caching, event-driven design, and the tradeoffs staff engineers navigate in production.
Java-specific algorithms and data structures at the senior level. Trees, graphs, dynamic programming, and concurrency — implemented idiomatically in Java.
STAR-method coaching calibrated for senior engineers. Communicate leadership, scope, and cross-functional impact — not just individual technical contribution.
3 of 50+ questions — free preview
Three real questions from the pack — one per pillar. The full pack has 50+ with complete model answers, edge cases, and interviewer notes.
Implement a token bucket using a ConcurrentHashMap keyed by user ID, where each entry holds an AtomicLong token counter refilled by a ScheduledExecutorService. For multi-node deployments, replace local state with Redis + Lua scripts so the decrement-check-expire is atomic across the fleet.
Thread-safety awareness, distributed vs. single-node tradeoffs, knowledge of Redis atomic primitives, and the ability to discuss clock skew in distributed refill strategies.
Use HashMap for O(1) average-case lookups when key ordering is irrelevant. Choose TreeMap when you need sorted iteration or range queries (subMap, headMap) — its Red-Black tree backing gives O(log n) guaranteed. LinkedHashMap covers the middle ground: O(1) operations with insertion-order iteration.
HashMap: O(1) average / O(n) worst-case with hash collisions. TreeMap: O(log n) guaranteed, no collision concern. Senior candidates also mention ConcurrentSkipListMap as the thread-safe sorted alternative.
Senior engineers are expected to move under ambiguity without waiting for perfect information. A strong answer shows you gathered the fastest available signal, defaulted to a reversible choice, communicated uncertainty to stakeholders proactively, and updated your position when evidence changed.
Situation — name the ambiguity (missing data, deadline, org pressure). Task — your explicit ownership. Action — how you de-risked the call (spike, prototype, team consult). Result — outcome + what you'd do differently. Interviewers penalise answers that lack reflection or skip the uncertainty entirely.
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