•SYSTEM DESIGN
LinkedIn System Design Questions
Every system design problem candidates reported at LinkedIn between September 2025 and September 2026, most-asked first. Each one links to a full solution.
Problems
11
Candidate reports
18
Asked more than once
6
start here
Question type
11 HLD
Design a Top-K Ranking Service
Design a system that continuously computes the top K items from a very large event stream: for example the K most-viewed URLs, the K services with the most error logs in the last 5 minutes, the top 100 most active users in a…
Also worded as: Design a Top-K search words service · Design an exception monitoring system with top‑K
Design a Multi-Region Malicious-IP Detection System
Design a service that decides whether a request's source IP (or a URL shared on the platform) is malicious and returns a low-latency decision: allow, challenge, rate-limit or block. Signals come from application and network…
Also worded as: Design a malicious-URL checking service using an isMalicious API
Scale a NoSQL Key–Value Store to One Million QPS
Design a horizontally scalable distributed key-value store like DynamoDB or Cassandra, or scale a single-node store to a stated workload (e.g., 50M keys, 1M requests/sec, 50/50 reads and writes). Support get/put/delete with…
Also worded as: Design a scalable key-value store
Design a CI Job Scheduler with Live Build Output
Design a CI/CD platform like GitHub Actions or Jenkins. Source changes trigger pipelines of dependency-linked tasks (build, test, deploy) that run on a pool of workers with different capabilities. Users see live status and…
Also worded as: Design a CI/CD Task Scheduler
Design a Calendar System
Design a calendar service like Google Calendar. Users create, update and delete events (one-time and recurring), invite attendees who can accept or decline, view day/week/month/agenda views across time zones, share calendars, get…
Also worded as: Design a Global Calendar Service
Design a metrics platform without alerting
Design an internal metrics monitoring platform like Datadog or Prometheus. Agents on hosts and services emit metrics (counters, gauges, histograms with tags); the system ingests millions of data points per second, stores them as…
Also worded as: Design a company-wide monitoring system
Reduce Stale Listings in a Job Marketplace
Design a system that detects and resolves stale job postings in a large job marketplace. A listing may be stale because it was filled, closed on the employer's own site, abandoned, duplicated, or expired. Discuss the signals…
Collect and Query Recent User Activity
Design a system that collects user activity events and answers queries over recent periods, such as the number of actions a user performed in the last minute, hour or day, or activity within a time range and geographic area.…
Design a Ranked Social Feed with Hybrid Fan-Out
Design the home feed of a social network like Instagram or Twitter. Users create posts (text, photos, video), follow other users, and open a personalized feed of recent posts from people they follow, possibly mixed with global or…
Review a Web Application Architecture
You are given an existing architecture or design document (for example Client -> DNS -> Load Balancer -> Application Service -> Database, plus a call to a third-party API) that contains omissions and unsafe assumptions. Review…
Design scalable job scheduler and query dashboard
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…
Duplicate reports of the same problem are merged and counted.
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What system design questions does LinkedIn ask?
Candidates reported 11 distinct system design problems at LinkedIn between September 2025 and September 2026, including Design a Top-K Ranking Service, Design a Multi-Region Malicious-IP Detection System, Scale a NoSQL Key–Value Store to One Million QPS.
How to prepare for LinkedIn system design interview?
Start with the LinkedIn problems reported most often, work through each full solution, then practice explaining a design end to end under time pressure in a mock interview.
What is the difference between HLD and LLD at LinkedIn?
HLD (High-Level Design) focuses on system architecture, scalability, and component interactions. LLD (Low-Level Design) dives into class diagrams, API contracts, and database schemas. LinkedIn tests both.