prepare for these full-stack developer interview questions

We asked Rufat Khaslarov, Chief Software Engineer I at EPAM Anywhere, and a practicing technical interviewer, to share his take on the most common full-stack developer interview questions.

In my opinion, modern full-stack development is primarily about delivery. That’s why a full-stack developer should be able to deliver every single feature from end to end, including the frontend, backend, infrastructure, automation testing, and more.

Considering this, those looking for full-stack developer jobs should be ready to respond to the following interview questions.

Even if you’re a software engineer with 20 years of experience under your belt, you might still be asked to cover fundamentals like:

• Computer science essentials: algorithm complexities, data structures, programming paradigms
• Network fundamentals: protocols, routing, OSI, TCP/IP models
• Best practices: design patterns, principles
• OSes

Also, be ready to solve an algorithm task, explain your chosen solution, and suggest improvements.

A sample question:

• What happens when you type google.com into your browser address bar?

In addition to your primary programming language, it’s highly recommended that you master an additional language. The more languages you know, the more approaches and best practices you have access to.

For example, even if your potential employer is hiring Python developers, knowing JavaScript will be a bonus for you. If you've mastered JavaScript and Python, learn Go and Rust, then try some frontend/backend framework combinations. For instance, it might be React/Spring, Angular/Django, etc.

Sample questions:

• What are the latest updates of your programming language specification? Framework?
• How do JavaScript engines work under the hood?

It's essential to know how to test your code, from unit testing to end-to-end testing.

Climbing up the testing pyramid, explore the tools, set up an environment, and test your code using different approaches, such as TDD/BDD, AAA, FIRST for unit testing, integration testing, contracts testing, UI testing, and performance testing.

You also want to refresh your skills with tools related to different technologies. For instance, if you work with JavaScript, be ready to use Jest, Mocha, and Chai libraries; for BDD you might need Cucumber; for e2e testing –– Cypress, Webdriver, and Protractor.

Sample questions:

• TDD vs BDD: What's the difference?
• What are the best practices for writing unit tests?

This set of full-stack engineer interview questions may include service development and communication protocols. You'll need to dive into HTTP and real-time communication (web sockets, polling).

Then, move on to architecture styles of web services: REST, RPC (gRPC), check GraphQL, and be ready to cover the pros and cons of using each. Also, provide the definitions of SOA, monolith, and microservice architecture.

On top of that, make sure you know how to document (for instance, swagger-like tools), debug, monitor, and deploy your services (containerization, orchestration). Additional topics might be:

• Authentication/authorization (OpenID, JWT, Oauth, and so on)
• Caching strategies
• Availability, reliability, and fault tolerance techniques

A sample question:

• Explain the differences between Rest API and GraphQL. What are the pros and cons of each?

You also need to understand and be ready to explain the following topics:

• Data abstraction layers (ORM, ODM, query builders)
• Differences between Relational and NoSQL databases
• Theoretical knowledge, including CAP theorem
• Transaction models (ACID/BASE)
• Data modeling and query optimization (indexes, aggregation, projections, functions, normalization)
• Replication and sharding
• SQL basics

Sample questions:

• How can we achieve data normalization? What are the types of normalizations (1NF, 2NF and so on)?

Clouds have taken over the infrastructure domain over the last few years, and have become almost the default choice for all cases and software solutions. So, prepare to cover at least the primary services of cloud providers (AWS, GCP, Azure are the most in-demand ones). Also, try to use them in your pet projects since they all provide free tier accounts.

Make sure you understand cloud distribution models (IaaS, PaaS, SaaS) and the pros/cons of using cloud providers. Explore serverless architecture and the components that you need to use (functions, message brokers, databases, storage).

Other major topics that may be a part of the interview are access management, deployment strategies (Blue-green, canary, etc.), alerting, and monitoring services.

A sample question:

• Please provide an example of the pillars of a well-architected framework in AWS.

This term includes web and mobile development. Whichever you’ve chosen, dig deeper into it.

For instance, if it’s web development, learn one of the most popular frontend frameworks (React, Angular or Vue), and know all related topics well (state management, client-side/server-side rendering). Learn how browsers work, and how they render pages, along with loading and rendering optimization techniques and principles (such as CRP and RAIL model).

You should be able to write HTML/CSS code as well. Progressive web apps (app shell, PRPL, service workers) and static site generators (like GatsbyJS) are trending now.

A sample question:

• Your customer’s website takes 10 seconds to load. What are you going to do to solve this?

You might be asked about working with requirements (DoR, DoD), documentation, code review, CI/CD, and release strategies on your current and past projects.

In addition, it's important to read about software development methodologies (Agile, Waterfall, and their combinations), and estimations (by analogy, by experts, planning poker, decomposition, bucket, t-shirt, story points).

Sample questions:

• Could you please describe the entire feature life cycle on your previous project? Do you think that the CI pipeline was flawless? Is there something that you'd change on your project?

I want to point out one more critical thing: try to break down each topic to its core and explain it in connection to your own experience. Of course, it's impossible to know everything, but you should explore and read at least key points related to the above topics.

Good luck with your interview!