Top Software Engineer Interview Questions 2026

Updated 12 days ago · By SkillExchange Team

1,696

Open Positions

$160,995

Median Salary

18

Questions

Preparing for software engineer interviews in 2026 means gearing up for a competitive landscape where software engineer jobs are abundant, especially remote software engineer jobs and software engineer jobs near me. With 1696 openings listed across top companies like Hopper, Bitwiseinvestments, BDG, Moment, and Gynger, the job outlook is strong. Salaries range from $3,000 to $550,000 USD, with a median of $160,995, making it an exciting time to break in, whether you're eyeing entry level software engineer positions or full stack software engineer roles.

What does a software engineer do? They design, develop, and maintain software systems, often collaborating in agile teams on everything from web apps to AI-driven platforms. Unlike the software engineer vs developer debate, where developers might focus more on coding, software engineers emphasize the full lifecycle, including architecture and optimization. If you're wondering how to become a software engineer, paths include a software engineer degree, bootcamps, or self-taught routes via software engineer bootcamps. Entry level software engineer salary often starts around $80K-$120K, depending on location and skills.

This guide delivers practical interview prep with 18 real-world questions balanced by difficulty, sample answers, and tips. Whether you're applying for software engineer jobs entry level, remote software engineering jobs, or senior positions at places like Alarm.com or Aurora-dev, you'll find scenarios mirroring actual interviews. We've woven in software engineer job description elements like problem-solving and system design. Avoid pitfalls in software engineer vs software developer confusion by focusing on engineering principles. Dive in to boost your chances in this thriving field.

beginner Questions

Explain the difference between == and === in JavaScript.

beginner
In JavaScript, == performs type coercion before comparison, so '5' == 5 is true. === checks value and type strictly, so '5' === 5 is false. Use === to avoid unexpected bugs from coercion.
Tip: Practice with real examples in your browser console to see coercion in action.

What is the output of console.log(0.1 + 0.2 === 0.3)? Why?

beginner
False. JavaScript uses IEEE 754 floating-point, causing precision loss: 0.1 + 0.2 is approximately 0.30000000000000004, not exactly 0.3.
Tip: Mention libraries like decimal.js for precise decimals in financial apps.

Describe RESTful APIs and HTTP methods.

beginner
REST uses HTTP for stateless communication. GET retrieves, POST creates, PUT/PATCH updates, DELETE removes resources. Use status codes like 200 OK, 404 Not Found.
Tip: Relate to a software engineer job description: APIs power most modern web services.

What are closures in JavaScript? Give an example.

beginner
Closures let inner functions access outer scope variables. Example: 
function outer() {
  let count = 0;
  return function inner() {
    count++;
    return count;
  };
}
const counter = outer();
console.log(counter()); // 1
Tip: Common in modules; explain for entry level software engineer interviews.

Differentiate let, const, and var.

beginner
var is function-scoped, hoisted. let and const are block-scoped, not hoisted. const can't be reassigned but allows mutation of objects.
Tip: Use let/const by default in modern codebases.

What is Big O notation? Examples of O(1), O(n), O(n^2).

beginner
Big O describes time/space complexity. O(1) is constant (array access), O(n) linear (loop), O(n^2) quadratic (nested loops). Crucial for scalable software.
Tip: Tie to real-world: Optimize loops for software engineer jobs remote apps.

intermediate Questions

Implement a function to reverse a string without built-ins.

intermediate
function reverseString(str) {
  let reversed = '';
  for (let i = str.length - 1; i >= 0; i--) {
    reversed += str[i];
  }
  return reversed;
}
Handles 'hello' -> 'olleh'.
Tip: Discuss two-pointer approach for arrays to show optimization thinking.

Find first non-repeating character in a string.

intermediate
Use hash map for counts, then iterate: 
function firstNonRepeating(str) {
  const map = {};
  for (let char of str) {
    map[char] = (map[char] || 0) + 1;
  }
  for (let char of str) {
    if (map[char] === 1) return char;
  }
  return null;
}
Tip: Time: O(n), Space: O(1) if charset limited. Great for full stack software engineer roles.

Explain promises vs async/await.

intermediate
Promises handle async with .then/.catch. Async/await is syntactic sugar: cleaner for chains. Example: async function fetchData() { try { const data = await fetch(url); } catch(e) {} }.
Tip: Convert promise chains to async/await in interviews for readability.

Design a URL shortener like bit.ly.

intermediate
Use base62 encoding on counter ID. Store mapping in DB. Handle collisions with unique IDs. Redirect via 301. Scale with sharding.
Tip: Cover hashing, DB design; relevant for software engineer job outlook in startups.

What is SQL injection? How to prevent?

intermediate
Attack via unescaped user input in queries. Prevent with prepared statements/parametrized queries, e.g., PDO in PHP or mysql2 in Node.
Tip: Demo safe query: Mention OWASP top 10 for security-focused jobs.

Merge two sorted linked lists.

intermediate
class ListNode { constructor(val, next) { this.val = val; this.next = next; } }
function mergeTwoLists(l1, l2) {
  if (!l1) return l2;
  if (!l2) return l1;
  if (l1.val < l2.val) {
    l1.next = mergeTwoLists(l1.next, l2);
    return l1;
  } else {
    l2.next = mergeTwoLists(l1, l2.next);
    return l2;
  }
}
Tip: Recursive is elegant; iterative saves stack for long lists.

advanced Questions

Design a LRU Cache.

advanced
Use HashMap + Doubly Linked List. Get/put in O(1): Map for key-node, move to head on access, evict tail. Implement get(key), put(key, value).
Tip: Draw diagram; crucial for remote software engineering jobs at scale.

Explain CAP theorem. Trade-offs?

advanced
CAP: Consistency, Availability, Partition tolerance. Pick 2. CP (consistent, partition-tolerant, e.g., Mongo with strong consistency), AP (available, partition-tolerant, e.g., Cassandra).
Tip: Relate to microservices in software engineer vs computer science discussions.

Rate limiter for API (100 req/min per IP).

advanced
Token bucket or sliding window. Redis: Increment counter with expire. if (count > 100) reject. Distributed with Lua scripts.
Tip: Handle edge cases like bursts; key for high-traffic apps at NeueHealth.

Find median of two sorted arrays.

advanced
Binary search for partition: O(log(min(m,n))). Ensure left max <= right min. Implement findMedianSortedArrays(nums1, nums2).
Tip: Practice on LeetCode; shows advanced algo skills for senior roles.

System design: Design Twitter.

advanced
Services: Timeline (fanout on write for celebs), User feed (pull), Storage (Cassandra for tweets, S3 for media). Caching (Redis), Search (Elasticsearch). Scale with sharding.
Tip: Clarify requirements first (QPS, features); use for software engineer degree holders.

Difference between TCP and UDP. When to use each?

advanced
TCP: Reliable, ordered, connection-oriented (HTTP). UDP: Fast, unreliable, connectionless (video streaming). Use UDP for low-latency like games.
Tip: Discuss congestion control; vital for network-heavy software engineer jobs.

Preparation Tips

1

Practice coding on LeetCode/HackerRank daily, focusing on medium/hard for software engineer jobs entry level and beyond.

2

Mock interviews via Pramp or friends; simulate remote software engineer jobs pressure.

3

Review system design primers like Grokking the System Design Interview for advanced rounds.

4

Build portfolio projects showcasing full stack software engineer skills, deploy to Vercel/Netlify.

5

Research company tech stack (e.g., Hopper's React/Node) to tailor answers.

Common Mistakes to Avoid

Not verbalizing thought process during coding; interviewers want reasoning.

Ignoring edge cases like empty inputs or max values.

Overcomplicating simple problems; keep solutions clean.

Failing to optimize after basic solution; discuss time/space.

Not asking clarifying questions in system design, assuming requirements.

Related Skills

System DesignData Structures & AlgorithmsCloud Computing (AWS/GCP)DevOps (Docker/Kubernetes)Frontend (React/Vue)Backend (Node/Python/Go)Databases (SQL/NoSQL)Testing (Unit/E2E)

Top Companies Hiring Software Engineer Professionals

Hopper (10)Bitwiseinvestments (9)BDG (6)Moment (5)Gynger (5)NeueHealth (5)Alarm.com (5)Artera (5)Aurora-dev (5)Aviyatech (5)

Explore More About Software Engineer

Software Engineer Career Guide
Career path and growth for Software Engineer
Software Engineer Resume Guide
Resume tips for Software Engineer professionals

Frequently Asked Questions

How long to prepare for software engineer interviews?

3-6 months for entry level software engineer, focusing on DSA and projects. Intensive bootcamps can accelerate.

Do I need a software engineer degree?

Not always; many land jobs via bootcamps or self-study, but degrees help for software engineer jobs near me at enterprises.

What's the software engineer vs software developer difference?

Minimal; engineers focus on full lifecycle, developers on coding. Titles overlap in job descriptions.

Are remote software engineering jobs common in 2026?

Yes, with strong demand at companies like Moment and Aviyatech offering flexibility.

What salary to expect for entry level software engineer?

$80K-$140K USD base, varying by location and company like BDG or Artera.

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