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Common technical interview questions for software engineering roles covering algorithms, system design, and code quality.
8 questions with expert tips
Practice with AI →Explain the time and space complexity of merge sort vs quicksort. When would you choose one over the other?
Expert Tip
Discuss O(n log n) average for both, but quicksort's O(n²) worst case and why merge sort is preferred for stable sorting.
Design a URL shortener like bit.ly. Walk through the full system architecture.
Expert Tip
Cover hashing strategy, database choice (SQL vs NoSQL), caching layer (Redis), load balancing, and analytics.
What is the difference between a generator and an iterator in Python? Provide a practical use case.
Expert Tip
Generators use yield and are lazy; iterators implement __iter__ and __next__. Use generators for large datasets.
Explain ACID properties. How does PostgreSQL ensure consistency during concurrent transactions?
Expert Tip
Cover Atomicity, Consistency, Isolation, Durability and explain MVCC (Multi-Version Concurrency Control).
You're asked to add a new payment method to a system that currently has 5 if/elif blocks. How do you refactor it?
Expert Tip
Strategy pattern: create a PaymentProcessor interface with concrete implementations. Register strategies in a dictionary.
How would you design a notification system that handles 10 million daily pushes across email, SMS, and push?
Expert Tip
Message queue (Kafka/SQS), separate workers per channel, rate limiting per provider, retry with exponential backoff.
Given an infinite stream of integers, how do you find the median at any point in time?
Expert Tip
Two heaps: max-heap for lower half, min-heap for upper half. Keep sizes balanced within 1 element.
Explain Python's GIL. How does it affect multi-threaded programs and what are the workarounds?
Expert Tip
GIL prevents true parallelism for CPU-bound tasks. Use multiprocessing module or async/await for I/O-bound work.
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