Software Engineer Interview Questions: 40+ Technical & Behavioral Questions for 2026

TL;DR: Software engineer interviews in 2026 test three distinct skill sets: algorithmic coding, system design, and behavioral competency. This guide covers 40+ real questions across all three categories with approach hints, frameworks, and preparation strategies. Whether you are targeting FAANG, a high-growth startup, or a mid-size company, the question patterns are predictable and the preparation is systematic. Treat your interview prep like a sprint — focused, time-boxed, and deliberate.

The Modern Software Engineer Interview Structure

Before diving into specific questions, it helps to understand the typical interview pipeline. While every company customizes their process, the structure follows a remarkably consistent pattern across the industry.

Phase 1: Recruiter Screen (15-30 Minutes)

A recruiter or talent partner calls to verify basic qualifications, discuss compensation expectations, and explain the interview process. This is not a technical evaluation, but it is a filter — candidates who cannot clearly articulate their experience or demonstrate genuine interest are screened out. Have a concise version of your career story ready and make sure your resume passes ATS screening before applying.

Phase 2: Technical Phone Screen (45-60 Minutes)

You will share your screen (or use a collaborative coding tool like CoderPad or HackerRank) and solve 1-2 coding problems in real time. The interviewer evaluates your problem-solving process, code quality, communication, and ability to handle hints or pivot when stuck. This round eliminates roughly 50-60% of candidates.

Phase 3: On-Site Loop (3-5 Interviews, 4-6 Hours)

The on-site (or virtual on-site) is the main event. Depending on the company and seniority level, expect a mix of:

• 2-3 coding rounds: algorithmic problems of medium-to-hard difficulty
• 1 system design round: architect a scalable system from scratch (for mid-level and above)
• 1 behavioral round: leadership, collaboration, conflict resolution, and culture fit

Some companies add a "culture fit" lunch or a practical coding exercise (pair programming, debugging a real codebase, or reviewing a pull request).

Coding Interview Questions by Topic

Coding questions test your ability to break down problems, choose appropriate data structures and algorithms, write clean code, and analyze complexity. Below are 15 representative questions organized by topic, each with approach hints to guide your thinking.

Arrays and Strings (5 Questions)

1. "Given an array of integers, find two numbers that add up to a specific target. Return their indices."

Approach hint: The brute force is O(n^2). Think about what data structure lets you look up a complement in O(1). A hash map that stores each number's index as you iterate gives you an O(n) solution in a single pass.

2. "Given a string, find the length of the longest substring without repeating characters."

Approach hint: Sliding window technique. Maintain two pointers and a set of characters in the current window. When you encounter a duplicate, shrink the window from the left until the duplicate is removed. Track the maximum window size throughout.

3. "Merge two sorted arrays into one sorted array in-place."

Approach hint: Start from the end of both arrays and work backwards. This avoids the need for extra space and prevents overwriting values you still need.

4. "Given a matrix of m x n integers, return all elements in spiral order."

Approach hint: Maintain four boundaries (top, bottom, left, right) and traverse in order: left-to-right across the top row, top-to-bottom along the right column, right-to-left across the bottom row, bottom-to-top along the left column. Shrink boundaries after each traversal.

5. "Determine if a string is a valid palindrome, considering only alphanumeric characters and ignoring cases."

Approach hint: Two pointers from each end, skipping non-alphanumeric characters. Compare characters after converting both to lowercase. O(n) time, O(1) space.

Trees and Graphs (5 Questions)

6. "Given a binary tree, determine its maximum depth."

Approach hint: Classic recursion. The depth of a tree is 1 + max(depth of left subtree, depth of right subtree). Base case: null node returns 0. Can also be solved iteratively with BFS using a queue.

7. "Validate whether a binary tree is a valid binary search tree (BST)."

Approach hint: Recursive approach with min/max bounds. Each node must fall within a valid range. Pass updated bounds down: for the left child, the current node becomes the upper bound; for the right child, it becomes the lower bound.

8. "Given an undirected graph, determine if it contains a cycle."

Approach hint: Use DFS with a visited set and a parent tracker. If you encounter a visited node that is not the parent of the current node, a cycle exists. For directed graphs, use three-color marking (white, gray, black).

9. "Find the shortest path between two nodes in an unweighted graph."

Approach hint: BFS is the standard approach for shortest path in unweighted graphs. Use a queue and track distances. For weighted graphs, switch to Dijkstra's algorithm.

10. "Serialize and deserialize a binary tree."

Approach hint: Use pre-order traversal for serialization, recording null nodes with a sentinel value. For deserialization, process the serialized string recursively, consuming one value at a time. Think about what information you need to reconstruct the tree unambiguously.

Dynamic Programming (3 Questions)

11. "Given a staircase with n steps where you can climb 1 or 2 steps at a time, how many distinct ways can you reach the top?"

Approach hint: This is essentially the Fibonacci sequence. ways(n) = ways(n-1) + ways(n-2). Start with the recursive solution, identify overlapping subproblems, then optimize with memoization or bottom-up DP. Space can be optimized to O(1) since you only need the previous two values.

12. "Given a set of coin denominations and a target amount, find the minimum number of coins needed to make that amount."

Approach hint: Classic DP. Create an array dp[0...amount] where dp[i] represents the minimum coins needed for amount i. For each amount, try every coin denomination and take the minimum. Initialize dp[0] = 0 and everything else to infinity.

13. "Given a string, find the length of the longest palindromic subsequence."

Approach hint: 2D DP where dp[i][j] represents the longest palindromic subsequence in the substring from index i to j. If characters match, dp[i][j] = dp[i+1][j-1] + 2. If they do not match, dp[i][j] = max(dp[i+1][j], dp[i][j-1]).

System Design-Adjacent Coding (2 Questions)

14. "Design and implement an LRU (Least Recently Used) cache with O(1) get and put operations."

Approach hint: Combine a hash map with a doubly linked list. The hash map provides O(1) lookup. The linked list maintains order: most recently used at the head, least recently used at the tail. On get, move the node to the head. On put, add to head and evict from tail if over capacity.

15. "Implement a rate limiter that allows at most N requests per second per user."

Approach hint: Several approaches: token bucket, sliding window counter, or sliding window log. For interviews, the sliding window approach using a queue of timestamps per user is clean and easy to explain. On each request, remove timestamps older than 1 second, then check queue size against N.

System Design Questions (12 Questions)

System design interviews evaluate your ability to architect scalable, reliable, and maintainable systems. These questions are typically asked at the mid-level (3+ years of experience) and above. There is no single correct answer — interviewers evaluate your thought process, trade-off analysis, and communication.

The Framework for System Design Answers

Use this four-step structure for every system design question:

1. Clarify requirements (3-5 minutes): Ask about scale (users, requests per second, data volume), features to prioritize, latency requirements, and consistency vs availability trade-offs.
2. Estimate scale (2-3 minutes): Back-of-envelope calculations for storage, bandwidth, and QPS. This demonstrates engineering rigor.
3. High-level design (10-15 minutes): Draw the major components: clients, load balancers, application servers, databases, caches, message queues. Explain data flow.
4. Deep dive (10-15 minutes): The interviewer will ask you to go deeper on specific components. Be ready to discuss database schema, caching strategy, sharding, replication, or failure handling.

Common System Design Questions

1. "Design a URL shortener (like bit.ly)."

Key considerations: Hashing strategy (base62 encoding vs MD5 truncation), collision handling, read-heavy workload (caching layer), database choice (key-value store), analytics tracking, and URL expiration policies.

2. "Design a Twitter/X-like social media feed."

Key considerations: Fan-out on write vs fan-out on read, hybrid approach for celebrities, timeline caching with Redis, tweet storage and indexing, follower graph storage, real-time notifications via WebSockets or SSE.

3. "Design a chat application (like WhatsApp or Slack)."

Key considerations: WebSocket connections for real-time messaging, message ordering and delivery guarantees, group messaging fan-out, presence/status tracking, message storage and history retrieval, end-to-end encryption architecture.

4. "Design a video streaming platform (like YouTube)."

Key considerations: Video upload and transcoding pipeline, adaptive bitrate streaming, CDN distribution, recommendation system at a high level, comment and engagement system, content moderation pipeline.

5. "Design a ride-sharing service (like Uber)."

Key considerations: Real-time location tracking and geospatial indexing (QuadTree or geohash), matching algorithm, ETA estimation, pricing engine (surge pricing), trip lifecycle management, driver and rider rating system.

6. "Design a distributed key-value store."

Key considerations: Consistent hashing for partitioning, replication strategy (leader-follower or leaderless), conflict resolution (vector clocks, last-write-wins), gossip protocol for node discovery, read/write quorums for tunable consistency.

7. "Design a web crawler."

Key considerations: URL frontier management (priority queue with politeness constraints), distributed architecture with worker nodes, deduplication (URL normalization and content hashing), robots.txt compliance, handling dynamic content (JavaScript rendering).

8. "Design a notification system."

Key considerations: Multi-channel delivery (push, email, SMS, in-app), priority and rate limiting, template management, delivery tracking and retry logic, user preference management, message queues for decoupling.

9. "Design an e-commerce search system."

Key considerations: Inverted index (Elasticsearch), relevance ranking (TF-IDF, learning to rank), autocomplete and suggestions, faceted search, personalization layer, handling real-time inventory updates.

10. "Design a rate limiter for an API gateway."

Key considerations: Algorithm selection (token bucket, sliding window, fixed window), distributed rate limiting with Redis, per-user and per-endpoint limits, response headers for clients, graceful degradation vs hard rejection.

11. "Design a file storage system (like Google Drive or Dropbox)."

Key considerations: Block-level deduplication, sync conflict resolution, chunked upload/download for large files, metadata service, change notification system, sharing and permissions model.

12. "Design a metrics monitoring and alerting system."

Key considerations: Time-series database selection, data ingestion pipeline (push vs pull model), aggregation and downsampling strategies, alert rule evaluation engine, dashboard query optimization, retention policies.

Behavioral Questions for Software Engineers (12 Questions)

Technical skills get you to the final round. Behavioral skills determine whether you get the offer. Engineering behavioral questions specifically evaluate how you collaborate in a technical environment, handle ambiguity, and grow as an engineer.

Technical Collaboration

1. "Tell me about a time you had a technical disagreement with a colleague. How did you resolve it?"
2. "Describe a situation where you had to convince your team to adopt a new technology or approach."
3. "Give me an example of when you had to work with a codebase you were unfamiliar with."
4. "Tell me about a time you helped a junior engineer grow. What was your approach?"

Problem-Solving Under Pressure

1. "Describe a production outage you were involved in resolving. What was your role?"
2. "Tell me about a time you had to make a significant technical decision under time pressure."
3. "Give me an example of when you had to debug a particularly difficult issue. Walk me through your process."
4. "Tell me about a project where the requirements changed significantly during development."

Growth and Ownership

1. "Describe a technical mistake you made. What happened and what did you learn?"
2. "Tell me about a time you proactively identified and fixed a technical debt issue."
3. "Give me an example of when you had to balance building the ideal solution with shipping on time."
4. "Tell me about a project you are most proud of. Why?"

For a deeper dive on behavioral interview preparation, including the STAR method, Story Bank technique, and fully worked answer examples, see our comprehensive behavioral interview questions guide.

How FAANG Interviews Differ from Startup Interviews

The same candidate can excel at one type of interview and struggle at another. Understanding the differences helps you allocate your preparation time effectively.

FAANG and Large Tech Companies

• Coding rounds: Heavy emphasis on algorithmic problem-solving. Expect 2-3 rounds of LeetCode-style problems ranging from medium to hard difficulty. Data structures and algorithms knowledge is non-negotiable.
• System design: Formal system design round for anyone at the mid-level or above. Interviewers have rubrics and evaluate specific criteria: scalability, fault tolerance, data modeling, and trade-off articulation.
• Behavioral: Structured behavioral rounds with standardized scoring. Amazon maps to Leadership Principles. Google evaluates Googleyness. Meta looks for impact orientation.
• Process: Highly standardized. Interviewers are trained, questions are calibrated, and the debrief follows a formal protocol. The process typically takes 4-8 weeks from initial screen to offer.

Startups and Mid-Size Companies

• Coding rounds: More practical and less algorithmic. You might debug a real bug in the codebase, implement a small feature, or pair program with a team member on an actual task. Take-home projects (4-8 hours) are common.
• System design: Less formal but still present for senior roles. Questions tend to be more grounded in the company's actual technical challenges: "How would you design the data pipeline for our product?"
• Behavioral: Often woven into technical discussions rather than a separate round. Culture fit is evaluated more holistically. The CEO or CTO may be involved for smaller startups.
• Process: Faster and more flexible. 2-4 weeks is typical. You may negotiate process adjustments (e.g., replacing a take-home with a live coding session).

How to Allocate Your Prep Time

If targeting FAANG, spend 60% of your time on algorithmic coding, 25% on system design, and 15% on behavioral preparation. If targeting startups, shift to 40% practical coding, 20% system design, 20% behavioral, and 20% on understanding the company's product and tech stack.

Resources for Practice

Consistent daily practice matters more than total hours. Here are the most effective resources organized by category.

Coding Practice

• LeetCode: The industry standard for coding interview practice. Focus on the "Top 150 Interview Questions" list and work through problems by topic rather than difficulty. Aim for 2-3 problems per day.
• HackerRank: Particularly useful for practicing timed assessments, since many companies use HackerRank for their online coding screen.
• NeetCode: Curated list of problems organized by pattern (sliding window, two pointers, backtracking, etc.). Excellent for building pattern recognition.

System Design

• System Design Interview books: Alex Xu's two-volume series is the most widely recommended resource for structured system design preparation.
• Engineering blogs: Read architecture posts from Netflix, Uber, Airbnb, and Stripe. These give you real-world context for system design patterns.
• Practice with peers: System design benefits enormously from practice with another person who can play the interviewer role and ask follow-up questions.

Behavioral Preparation

• JobJourney AI Interview Coach: Simulates real behavioral and technical interview scenarios with instant feedback on your STAR structure and communication clarity.
• Story Bank preparation: Write out 8-10 career stories in STAR format covering leadership, conflict, failure, and collaboration. Practice delivering them in 2-3 minutes each.

Preparation Timeline: 6-Week Plan

Here is a structured plan for software engineer interview preparation:

Weeks 1-2: Foundation

• Solve 3 LeetCode problems daily (easy to medium), focusing on arrays, strings, hash maps, and two pointers
• Review data structures: arrays, linked lists, trees, graphs, hash maps, heaps, stacks, queues
• Start writing your Story Bank (target 8-10 stories)
• Update your resume — use software engineer resume examples for reference and run it through our ATS checker

Weeks 3-4: Intermediate

• Move to medium and medium-hard problems. Focus on trees, graphs, dynamic programming, and backtracking
• Start system design study: learn the building blocks (load balancers, caches, databases, message queues)
• Design one system per day from the list above
• Practice behavioral answers out loud — use AI interview practice for structured feedback

Weeks 5-6: Mock Interviews and Refinement

• Do 2-3 full mock interviews per week (coding + system design + behavioral)
• Focus on weak areas identified during mocks
• Practice under time pressure: 30 minutes per coding problem, 35 minutes per system design question
• Finalize your cover letter for target companies

Key Takeaways

1. Software engineer interviews test three distinct skills: algorithmic coding, system design, and behavioral competency. Prepare for all three, but allocate time based on whether you are targeting FAANG or startups.
2. For coding questions, focus on pattern recognition over memorization. The 10-12 core patterns (sliding window, two pointers, BFS/DFS, DP, etc.) cover the vast majority of interview problems.
3. System design has a clear framework: clarify requirements, estimate scale, draw the high-level architecture, then deep-dive. Practice 10-15 common designs until the process feels natural.
4. Behavioral questions matter more than most engineers think. Companies use behavioral rounds to differentiate between technically equal candidates. Prepare 8-10 STAR-formatted stories.
5. Daily practice over 4-8 weeks outperforms cramming. Solve 2-3 problems per day, design one system per day, and practice one behavioral story per day.
6. Use your resume as a tool for the interview, not just for getting it. Make sure the projects and skills on your resume align with what you are prepared to discuss in depth.

Prepare for Your Software Engineer Interview with JobJourney

Reading about interview questions is essential preparation, but practicing under realistic conditions is what builds confidence and performance. JobJourney's AI Interview Coach simulates the full software engineer interview experience — behavioral questions with STAR scoring, technical communication practice, and instant feedback on clarity and structure.

Before you apply, make sure your resume is optimized. Check out our software engineer resume writing guide for section-by-section advice, or browse software engineer resume examples for inspiration. Run your resume through our ATS Resume Checker to verify it will pass automated screening, and use our Cover Letter Generator to craft a compelling companion letter.

Engineers who practice with structured mock interviews are 2-3x more likely to pass their on-site loops. Start your preparation today.