Confluent system design interview questions

One question on this site is reported in Confluent software engineer interviews. Each has a full reference design (requirements, back-of-envelope numbers, components, user flows and deep dives with interviewer follow-ups). Each one can be walked through turn by turn and then sat as a mock. Patterns covered: append-only-log, partitioning, replication, consumer-groups, exactly-once.

Attribution comes from public interview guides and candidate reports, not from Confluent. It indicates where a question has been asked, nothing more.

hard

Design a Distributed Message Queue

A Kafka-style log that ingests a million messages a second, keeps them in order per key, replicates them so no acknowledged message is lost, and lets many consumer groups read at their own pace.

append-only-logpartitioningreplicationconsumer-groupsexactly-once

WalkthroughSign in Mock interviewPro Read the reference

How to prepare for a Confluent system design interview

Large-company loops run 45 to 60 minutes, expect numbers, and spend most of the time on deep dives. Walk through a question to see how a strong candidate paces the hour, sit the same question as a mock until you can produce the requirements, the estimates and the design without looking, then read the interview framework guide for how to structure the hour. The other questions on the site teach patterns that show up in Confluent interviews under different names.

Design a URL Shortenerkey-generation · caching · cdn
Design Slackreal-time · websockets · fan-out
Design a Payment Systemconsistency · idempotency · ledger
Design a News Feedfan-out · ranking · caching
Design YouTubetranscoding · cdn · adaptive-bitrate
Design Google Mapsgeospatial · routing · graphs
Design a Matchmaking Systemqueues · scheduling · latency
Design Ubergeospatial · matching · streaming
Design a Notification Systemfan-out · multi-channel · idempotency
Design Google Docscrdt · operational-transform · websockets
Design an LLM Inference Servicegpu-batching · streaming · scheduling
Design a Distributed Cacheconsistent-hashing · eviction · replication
Design a Web Crawlerfrontier · politeness · dedupe
Design a Rate Limiteralgorithms · counters · redis
Design Dropboxchunking · dedupe · sync
Design Ticketmasterinventory · reservations · locking
Design Search Autocompletetries · ranking · caching
Design an Ad Click Aggregatorstream-processing · windowing · exactly-once
Design a Distributed Job Schedulerscheduling · leases · idempotency
Design a Stock Exchangeorder-book · determinism · event-sourcing
Design a Project-to-Contractor Matching Systemrecommendations · ranking · marketplace
Design Instagrammedia-pipeline · object-storage · fan-out
Design WhatsApppersistent-connections · store-and-forward · end-to-end-encryption
Design Netflixcdn · proactive-caching · adaptive-bitrate
Design Yelpgeospatial-index · search · ranking
Design a Real-Time Leaderboardsorted-sets · ranking · sharding
Design a Distributed Key-Value Storeconsistent-hashing · quorum-replication · conflict-resolution
Design a Unique ID Generatorid-generation · clocks · leases
Design LeetCodesandboxing · job-queue · untrusted-code
Design Airbnbavailability-search · inventory · double-booking
Design a Metrics and Monitoring Systemtime-series · compression · cardinality
Design Tindergeo-sharding · recommendations · bloom-filters
Design Redditcomment-trees · voting · ranking
Design DoorDashstate-machine · dispatch · eta-prediction