LinkedIn Interview Questions
Practice 148 real LinkedIn interview questions for 2026. Covers all top categories — Coding & Algorithms, System Design, Analytics & Experimentation, Data Manipulation (SQL/Python), and Behavioral & Leadership — across Software Engineer, Data Scientist, Machine Learning Engineer, and Data Engineer roles. Real questions from actual interviews with detailed solutions; this collection is designed for focused interview preparation that prioritizes coding and scale-first problem solving alongside rigorous metrics thinking. Expect LinkedIn interviews to evaluate production-ready tradeoffs, clear metricization of ranking and relevance, and the ability to diagnose live-traffic regressions. For Software Engineer candidates, recurring themes include constant-time randomized data structures and frequency-weighted sampling, Top-K ranking service design and distributed-scaling considerations, plus classic array/string and stack-with-max algorithmic problems. Data Scientists should be ready for model fundamentals and optimization (logistic regression, backprop, Adam), causal and experimentation diagnostics for feed/homepage drops, and sampling/variance concerns in ranking metrics. Machine Learning Engineers will see recommendation and skills-inference system design, clustering convergence and probabilistic sampling questions, and production alerting/spike-detection. Data Engineers encounter efficient data-structure implementations tied to measurable production impact.
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Explain Logistic Regression, Backprop, and Adam
Answer the following machine learning fundamentals questions: 1. Logistic regression - Explain how logistic regression works for binary classificat...
Debug Queues and Solve Arrays
During the coding rounds, the interviewer asked several implementation problems: 1. Debug a priority queue. You are given an array-backed min-heap. Th...
Review a Web Application Architecture
You are given a high-level architecture diagram for a web application: Client/Web App -> DNS -> Load Balancer -> Application Service -> Database The a...
Scale a Distributed Randomized Multiset
After designing the randomized multiset on a single machine, explain how you would scale it across multiple servers. The distributed system should sup...
Explain iOS ARC and avoid retain cycles
iOS Memory Management (ARC) You have 10 minutes to explain iOS memory management under ARC. Cover the following: 1. How ARC manages object lifetime (w...
Design a Global Calendar Service
Design a calendar system for users in multiple time zones. The system should support: - creating, updating, deleting, and viewing calendar events - on...
Design a Top-K Ranking Service
Design a service that returns the top K most frequent items for a configurable time window, such as the top 10 search queries in the last hour or the ...
Implement an LRU cache with follow-ups
Coding: Implement an LRU Cache and discuss concurrency Design and implement an in-memory Least Recently Used (LRU) cache data structure. The cache sho...
Compute inverse-depth weighted sum of nested lists
Inverse-Depth Weighted Sum of a Nested List You are given a nested list of integers. Each element is either: - an integer, or - another nested list. D...
Handle Issues and Onboard Teammates
The manager and communication rounds focused on two prompts: 1. Tell me about a time you handled a cross-functional issue, operational incident, or di...
Sample index from weighted probability distribution
Given an array weights[0..M-1] representing a discrete distribution over M outcomes, implement a function sampleIndex(weights) that returns an index i...
Derive mean and variance of x̄
Let \(X_1, X_2, \dots, X_n\) be random variables, and define the sample mean as \(\bar X = \frac{1}{n}\sum_{i=1}^n X_i\). 1. Assume the variables are ...
Discuss Projects and Tradeoffs
You are asked to do a deep dive on two past software projects. For each project, explain: 1. The business or engineering problem. 2. Your exact role, ...
Design a malicious-URL checking service using an isMalicious API
Design a backend service that determines whether a given URL is malicious. You have access to an external dependency: - isMalicious(url) -> bool (blac...
Design a Randomized Multiset
Implement a data structure for integers that allows duplicate values and supports the following operations in expected O(1) time: - insert(val): Add o...
Find index with positive suffix sums
Given an unsorted integer array \(A\), find an index \(i\) such that every cumulative sum starting from \(i\) to the end of the array is strictly posi...
Compute article-type diversity per user and histogram
You track article views and article metadata. Tables article_views - user_id INT - article_id INT - view_date DATE articles - article_id INT (PK) - ar...
Generate uniform 0–6 from biased coin
You are given a function: - int getRandom01Biased() returns 0 with probability p and 1 with probability 1-p, where p is unknown and may be any value i...
Solve common string and subarray problems
You are given three coding tasks: 1) Reverse a string - Input: a string s. - Output: the string with characters in reverse order. 2) Maximum sum of a ...
Design a meeting scheduler API
Meeting Scheduler (OOD + data structures) Design and implement an in-memory meeting scheduler that stores existing bookings and can answer availabilit...