Free · No sign-up · English & Persian
Software engineering interview prep, from Junior to Senior
Pick a track, choose your level and practice multiple-choice questions with instant feedback and full explanations.
- practice questions
- 3,600+
- practice questions
- live tracks
- 3
- live tracks
- difficulty levels
- 3
- difficulty levels
- languages
- 2
- languages
What is the main difference between let/const and var?
- a
let/constare block-scoped;varis function-scoped - b
varonly works in strict mode - c
constmakes objects deeply immutable - dThey have no scoping difference
Correct answer, with a full explanation
Tracks
Choose the path that matches the role you are interviewing for.
Frontend
HTML & CSS, JavaScript, TypeScript, React, Next.js and frontend architecture
8 topics
Backend
Node.js, API design, databases, auth, caching, message queues and backend architecture
8 topics
System Design
Scalability, load balancing, replication, sharding and distributed systems
8 topics
Algorithms & Data Structures
Big O, arrays, hash maps, trees, graphs and dynamic programming
Software Engineering
OOP, SOLID, design patterns, clean code, testing and Git
DevOps & Cloud
Docker, CI/CD, Linux, Nginx, Kubernetes and monitoring
Behavioral
Teamwork, conflict, ownership and the STAR method for answering
How it works
DevTier is a free site for software engineering interview preparation. It has 3600 multiple-choice questions across 3 live tracks (frontend, backend and system design), split into Junior, Middle and Senior levels. Every question is available in English and Persian, and every answer comes with a full explanation so you learn the why, not just the answer.
- 1
Pick a track
Frontend, backend or system design, depending on the role you are interviewing for.
- 2
Choose your level
Junior for fundamentals, Middle for real-world scenarios and Senior for architecture and hard trade-offs.
- 3
Practice and learn
Pick an answer, see right away whether it is correct and read the explanation. Your progress is saved on this device.
Interview prep guides
In-depth guides on what each interview asks and how to prepare.
Junior vs Middle vs Senior Interviews: What Each Level Expects
How junior, middle and senior developer interviews differ: the same question at three depths, system design and behavioral expectations, and how to pick your level.
System Design Interview: A Step-by-Step Guide to Passing
Prepare for your system design interview with a proven 45-minute framework, estimation examples, core building blocks, a URL shortener walkthrough, and a study plan.
Backend Interview Guide: Node.js, APIs, Databases & More
A complete backend interview guide: Node.js event loop, API design, SQL and NoSQL, Redis caching, auth, message queues, a 4-week plan and level expectations.
From developers who practiced here
How developers used DevTier to get ready for their interviews.
The explanation behind each answer mattered more to me than the question itself. The event loop and closure questions I practiced here came up almost word for word.
The Junior, Middle and Senior split showed me exactly where I stood. The senior database and caching questions exposed my weak spots.
I never knew where to start with system design. The step-by-step guide and the trade-off questions finally gave me a structure.
I answered ten React questions every night. Two weeks later I could talk about re-renders and memoization with real confidence.
I was nervous about my first interview. Having questions in Persian while keeping the English terms was exactly what I needed.
Free, no sign-up, and it remembers my progress. Of everything I tried, this was the only resource I actually finished.
I now use DevTier to prepare interview questions for my own team. They are realistic and up to date.
Frequently asked questions
Who is DevTier for?
Developers preparing for technical interviews, from people looking for their first job to experienced engineers interviewing for senior roles.
Which topics are covered?
Frontend (HTML & CSS, JavaScript, TypeScript, React, Next.js and more), backend (Node.js, API design, databases, caching, security, message queues and more) and system design (scalability, load balancing, sharding, CAP, case studies and more). Algorithms, software engineering, DevOps and behavioral interviews are coming soon.
Is DevTier free? Do I need an account?
Yes, it is completely free and needs no sign-up. Your progress and bookmarks are stored only in your own browser.
Are the questions in English or Persian?
Both. You can switch languages at any time. The Persian text keeps technical terms in English, the way they are used at work.
What is the difference between Junior, Middle and Senior?
Junior questions test fundamentals, Middle questions focus on applied, real-world scenarios and Senior questions are about architecture, performance and trade-offs.
Ready for your next interview?
Pick a track and answer your first question right now. Free, no sign-up.
Start practicing