#memory

13 memory interview questions, asked at Microsoft, xAI, Amazon and 8 more companies. Last asked Oct 2026.

Check and insert among a million user IDsSystem designA service holds about a million user IDs. Each request carries a user ID: if it is not in the set yet, add it. Decide how to store the IDs and run this check-and-insert, and talk…
Last asked Oct 2026
Top-k prefix suggestions filtered by departmentCodingA service has a fixed list of suggestions, each (ngram, department, score). Implement getTopSuggestions(query, userDept, k), returning the k best-scoring suggestions that match…
Last asked Sep 2026
Copy a rectangle within a 2D array in placeCodingGiven a 2D array, a rectangular block (top-left corner, height, width) and a destination for its top-left corner, copy the block to the destination with O(1) extra memory. The…
Last asked Sep 2026
Components of an LLM agent's memoryML designName the common components of an LLM agent's memory (for example the context window, a short-term scratchpad or conversation buffer, long-term stores of facts and past episodes…
Last asked Sep 2026
Fast search over large autonomous-vehicle logsSystem designVehicles produce large raw logs and vehicle records. Design how engineers search them quickly, for example for every record that matches some conditions, when the data is far…
Last asked Aug 2026
Design a dictionary whose keys and values have mixed typesCodingDesign a key-value dictionary in which keys and values can be of different types and lengths. Explain how you hash and compare keys of different types, how collisions are handled…
Last asked Aug 2026
Firmware fundamentals: endianness, ring buffers and the stackCodingAnswer and code short firmware questions: what big- and little-endian mean and how to detect or convert byte order, how a ring buffer works between an interrupt handler and the…
Last asked Jul 2026
Nearest-center assignment without an N x K x D distance tensorCodingGiven N points and K centers in D dimensions, assign each point to its nearest center, as in the assignment step of k-means. The obvious broadcast builds an N x K x D array of…
Last asked Jul 2026
Design personalization memory for a chatbotAI system designDesign how an AI assistant remembers things about each user across conversations and uses them to personalize answers. Cover what to store and how it is extracted, retrieval at…
Last asked May 2026
Systems fundamentals quick-fire: memory, processes, threads and transactionsCodingA short screen of basics, answered out loud: 1. What an array is, how it is laid out in memory, and how it differs from a linked list. 2. What a smart pointer is and the kinds you…
Last asked Feb 2026
Implement memcpy with misaligned addressesCodingWrite memcpy: copy n bytes from a source address to a destination address. Copying one byte at a time is slow, so copy in machine words, and handle source and destination pointers…
Last asked Jan 2026
Design a string type: memory layout, moves and thread safetyCodingWhat is a string in a programming language? Describe what fields a string struct holds (for example in Rust: pointer, length, capacity) and how you would implement one yourself…
Last asked Jul 2025
How strings are stored and what copying them costsCodingWhat is a string under the hood? Describe the fields a string struct holds and how you would implement one yourself, then give the time cost of copying a string and of common…
Last asked Jul 2025