Company interview vault

Datadog Mid-level (3–5 years) Coding / DSA

#2401

Solve the 0/1 knapsack problem with dynamic programming — Datadog interview

Reported in Datadog USA engineering loops. Classic DP testing tabulation, space optimization, and item selection reconstruction.

Hard Read answer →

Datadog Mid-level (3–5 years) Coding / DSA

#2402

Design and implement an LRU cache with O(1) get and put — Datadog interview

Reported in Datadog USA engineering loops. Hash map plus doubly linked list problem bridging DSA and system components.

Hard Read answer →

Datadog Mid-level (3–5 years) Coding / DSA

#2403

How many distinct ways can you climb n stairs taking 1 or 2 steps at a time? — Datadog interview

Reported in Datadog USA engineering loops. Introductory dynamic programming problem isomorphic to Fibonacci.

Medium Read answer →

Roblox Mid-level (3–5 years) System design

#2404

Explain the CAP theorem and what it means for distributed systems — Roblox interview

Reported in Roblox USA engineering loops. Classic system design question asked at US big-tech and fintech on-site loops.

Medium Read answer →

Roblox Mid-level (3–5 years) Coding / DSA

#2405

How do you perform topological sort on a directed acyclic graph? — Roblox interview

Reported in Roblox USA engineering loops. Graph algorithm for task scheduling, build systems, and course prerequisites.

Medium Read answer →

Roblox Mid-level (3–5 years) Technical deep dive

#2406

What is dependency injection and why is it useful? — Roblox interview

Reported in Roblox USA engineering loops. Java/Spring staple connecting OOP design to testable service architecture.

Medium Read answer →

Roblox Mid-level (3–5 years) Technical deep dive

#2407

How do you version a public API without breaking clients? — Roblox interview

Reported in Roblox USA engineering loops. API evolution question covering compatibility, deprecation, and communication.

Medium Read answer →

Roblox Mid-level (3–5 years) Behavioral

#2408

Tell me about a project that failed or missed its deadline. What did you learn? — Roblox interview

Reported in Roblox USA engineering loops. Behavioral question testing accountability, retrospectives, and growth.

Medium Read answer →

Roblox Mid-level (3–5 years) Technical deep dive

#2409

Compare ACID and BASE consistency models in databases — Roblox interview

Reported in Roblox USA engineering loops. Distributed data question bridging SQL transactions and NoSQL eventual consistency.

Medium Read answer →

Roblox Mid-level (3–5 years) Technical deep dive

#2410

How does Node.js handle concurrent requests with a single thread? — Roblox interview

Reported in Roblox USA engineering loops. Node.js architecture question on libuv, event loop phases, and worker threads.

Medium Read answer →

Roblox Mid-level (3–5 years) Technical deep dive

#2411

When would you use useState versus useReducer in React? — Roblox interview

Reported in Roblox USA engineering loops. React hooks question on local state complexity and predictable updates.

Medium Read answer →

Roblox Mid-level (3–5 years) Technical deep dive

#2412

What is the Python GIL and how does it affect concurrency? — Roblox interview

Reported in Roblox USA engineering loops. Python-specific question on threading limits and multiprocessing alternatives.

Medium Read answer →

Roblox Mid-level (3–5 years) Technical deep dive

#2413

Explain the JavaScript event loop, call stack, and task queues — Roblox interview

Reported in Roblox USA engineering loops. Core JavaScript concurrency model question for frontend and Node.js roles.

Medium Read answer →

Roblox Mid-level (3–5 years) Technical deep dive

#2414

How does HashMap work internally in Java? — Roblox interview

Reported in Roblox USA engineering loops. Java-specific collections question on buckets, hashing, and resize behavior.

Medium Read answer →

Roblox Mid-level (3–5 years) Technical deep dive

#2415

What is the difference between unit and integration tests? — Roblox interview

Reported in Roblox USA engineering loops. Testing strategy question covering pyramid, mocks, and confidence vs speed.

Easy Read answer →