Databricks System Design Questions

Design Chat APIs, Storage, and Core Message Flows

Design a real-time chat system like WhatsApp or Slack supporting one-to-one and group conversations (and, for Slack variants, workspaces, channels and threaded replies). Users send and receive messages with low latency, see…

Also reported as: Design Chat Deletion Semantics Under Concurrent Sends · Design a Chat Application with a Partitioned Cache · Design a Slack-Like Messaging System +3 more

Design an Online Book Seller Platform

Design an online bookstore platform. Users browse and search books, see prices (aggregated from multiple external sellers or suppliers, with individual and batched price lookups), manage a cart, place orders, pay, and track order…

Also reported as: Design a Bookstore Pricing API with Batch Fetches · Design a Book Price Aggregator · Design an Online Bookstore +1 more

Design a Music Playlist Service

Design a music playlist service (and optionally music search and playback controls). Users create playlists, add and remove tracks (duplicates allowed), reorder items, and share collaborative playlists that several users edit…

Also reported as: Design a Collaborative Playlist Editor

Design a Durable Concurrent Event Writer

Design and implement a thread-safe event writer shared by thousands of producer threads that append opaque records to a single file. Producers should not block on slow disk I/O: writes go into an in-memory buffer that a dedicated…

Also reported as: Design a Thread-Safe Buffered Writer with a Background Flush Thread

Design a KV store with QPS API

Design and implement an in-memory key-value store that supports get(key), put(key, value) and delete(key), plus an API that reports the store's current throughput: the number of get and put operations in the last 5 minutes…

Also reported as: Design KV store with sliding-window QPS metrics

Design a Distributed File System

Design a distributed file system like GFS or HDFS that stores very large files across thousands of commodity machines. Support create, read, append/write, delete and directory operations with a hierarchical namespace.…

Design a stock order manager

Design a stock trading or brokerage platform like Zerodha or Robinhood. Users view real-time quotes, place orders (market, limit, stop), see order status and fills, and view holdings and balances. Orders are validated (buying…

Design a Hierarchical File System

Design a file system abstraction: an in-memory hierarchical file system supporting mkdir, ls, create file, write/append, read and delete on paths; then discuss how to persist it so that file contents and metadata are recovered…

Design a single-node persistent in-memory cache

Design and implement an LRU cache with fixed capacity and O(1) get/put (hash map plus doubly linked list). Then extend it: make it thread-safe for concurrent reads and writes in a web service, and make it crash-resilient so the…

Design CRUD APIs with async jobs

Design a backend service that provides CRUD APIs for a resource plus asynchronous background jobs that operate on those resources (e.g., long-running exports or processing). Clients create resources, trigger jobs, poll or…

Design a dependency-aware job scheduler

Design a distributed job scheduler that runs user-defined jobs at a specified time (one-time) or on a recurring cron schedule, at a scale of millions of jobs per day. Requirements: jobs fire close to their scheduled time, each…

Design a digital game shop backend

Design a digital game distribution platform like Steam: a game catalog, user libraries, purchases and refunds, promotions and discounts, entitlements (who owns what), license checks at launch, and delivery of large game downloads…