Uber | SDE-2 – Frontend Engineer | Interview Experience

🧠 Round 1 (Screening): Memoization + Data Structures Problem: Implement a memoize() utility with nested argument support using a trie-like structure.

Given a function, memoize it such that multiple arguments (primitives + refs) are cached correctly.

Required building a trie inside a Map to support nested argument caching.

Discussed time-space tradeoffs, argument uniqueness, and cache invalidation strategies.

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⚙️ Round 2: Async Execution with Limit Problem: Implement a scheduler that runs async tasks with a concurrency limit (like Promise.all with limit = 2).

I used a queue + counter mechanism to throttle concurrent executions.

Discussion included edge cases (failures, infinite queues) and performance under load.

Covered task queue backpressure and the role of microtasks vs macrotasks.

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🧩 Round 3: Task Runner with Dependencies Problem: Execute a set of async tasks with dependencies (like a build graph).

Input: tasks A–E with dependencies { D: ['A','B'], E: ['C','D'] }

Wrote a runTasks utility to resolve and run in order using a custom dependency resolver (not topo sort).

My approach worked but the interviewer hinted I should’ve used topological sorting.

⚠️ Feedback: Functional but the interviewer seemed unsatisfied without topo sort.