Employing experienced developers is essential to developing a successful technology team, but evaluating their technical expertise can be difficult. With so many programming languages, tools, and frameworks available, it can be challenging to know what questions to ask during a technical interview.
This article will discuss the best practices for evaluating the technical skills of seasoned developers, including the major areas to evaluate and the technical questions to ask. By the end of this article, you will have a good grasp of how to evaluate experienced developers successfully, allowing you to make educated hiring decisions and construct a high-performing tech team.
Technical Areas to Assess for Experienced Developers
Before we dive into questions for experienced developers, let’s look at some of the technical areas to focus on when designing code challenges.
Programming Languages and Tools
A senior programmer should be comfortable with a range of languages and tools and have experience with the specific technologies that your team uses. If your organization mostly works in embedded technologies, for example, you would prefer someone with a C++ or Rust programming language skillset.
Architecture and Design
Senior programmers should be able to design and implement complex systems and architectures that are scalable, maintainable and efficient. Your ideal candidates should have experience with architecture patterns, such as microservices and can explain their design decisions clearly. They should be skilled enough to make different architectural decisions. For example, should REST-based API’s be preferred over GraphQL-based API’s? Should caching be implemented on the front end or the back end?
Testing and Debugging
Senior programmers should have a deep understanding of testing and debugging techniques and should be able to write tests and diagnose problems effectively. A senior programmer should have experience with automated testing tools, API testing, load testing, debugging tools and penetration testing.
CI/CD Processes
While senior developers will not be implementing the CI/CD pipelines, they should have strong knowledge of how continuous integration and deployment work. They should understand different code merging techniques, code branching strategies, when to freeze code, what should be the release schedule and how to resolve merge conflicts.
Databases
Almost all modern distributed systems use a database in one form or another. A senior programmer should have a good understanding of database design and implementation. They should be able to design efficient database schemas, write complex queries, optimize slow queries and should have knowledge of database components like indexes, views and triggers. They should also know which RDBMS to select for a particular system and if NoSQL should be preferred over RDBMS for a particular application.
Performance and Optimization
Senior programmers should be able to optimize code for performance and efficiency and should be able to identify and resolve performance bottlenecks. The candidate should have experience with profiling and optimization tools and be familiar with best practices for performance optimization. They should have strong knowledge of load balancers, caching, lazy loading, ORM and different refactoring techniques.
Security
Senior programmers should be able to write secure code and follow best practices for security. The candidates should have experience with security frameworks and standards such as OAuth or JWT, OWASP and be familiar with common security vulnerabilities such XSS (Cross-site scripting) and CSRF (Cross-site request forgery).
Containerization
A senior programmer should have strong knowledge of docker containers and best practices for containerizing complex applications. As most modern applications are highly distributed in nature, the knowledge of implementing different containers for an application is also essential.
Microservices
Most modern high-tech systems are based on microservices instead of a monolith architecture. A senior developer should have experience in developing different microservices and knowledge of the inter-communication of different microservices in an application.
Data Structures and Algorithms
Senior programmers should have a deep understanding of data structures and algorithms and be able to apply them effectively. The candidate should be comfortable with complex data structures and algorithms and can explain their approach to solving problems. A good senior developer should have the skills to decide if one type of data structure should be preferred over another.
Communication and Teamwork
It is important to evaluate a senior programmer’s communication and teamwork skills. The candidate should be able to work effectively with others, communicate technical concepts clearly to non-technical stakeholders and mentor and lead junior team members.
Cloud Technology
As the majority of applications are now cloud-native, so it is critical for an experienced developer to have strong knowledge of different cloud-based vendors and their key services.
Questions for Experienced Developers
Here are some of the technical questions related to the above areas that should be asked for the evaluation of senior developers.
Software Architecture and Design Questions
1. What design patterns have you utilized in your projects, and how have they improved the system design?
2. How do you determine which design pattern to utilize for a certain situation, and what criteria do you take into account?
3. How do you approach developing a software architecture for a SaaS-based web application, and what best practices have you implemented in your projects?
4. Can you describe typical microservices, monolithic, and event-driven software architecture patterns?
5. How are scalable and performant systems designed, and what are the best techniques for doing so?
6. How do your designs address latency, network bandwidth, and database performance issues?
7. What use cases are ideal for using a content delivery network (CDN)?
8. How do you determine whether caching should be done on the back or front end?
9. What are the best techniques for designing and modeling data for a web application?
10. How do you incorporate APIs and third-party services into your designs, and what best practices have you applied in this regard?
11. Describe common integration patterns such as point-to-point, publish-subscribe, and asynchronous messaging.
12. How do you address design concerns associated with system downtime, network outages, and other sorts of failures?
13. When do you prefer vertical scaling over horizontal scaling or vice versa?
Databases
1. Can you suggest some guidelines that you have implemented for designing a normalized database schema?
2. Can you describe the difference between a schema-less and a schema-on-read database and when one should be preferred over the other?
3. Is it true that a subquery (or inner query) always slows down the performance? If yes, what is the alternate?
4. How do you use SQL to aggregate data, such as calculating averages, sums, and counts?
5. Can you give at least two business use cases where a NoSQL is preferred over a relational database?
6. Can you describe the difference between a document-oriented and a key-value NoSQL database and which one you have used in your projects?
7. How do you ensure a database’s high availability and fault tolerance in a production environment?
8. Can you describe the difference between hot and cold backups and when each is appropriate?
9. What are some best practices for securing a database and protecting sensitive data?
10. Can you advise on some database optimization techniques to improve the speed of query execution?
11. Can you describe the difference between indexing and partitioning based on your experience?
12. How do you handle performance bottlenecks in database systems, such as network latency, disk I/O, and query optimization?
13. What are some common data integration tools, such as Apache Kafka and Apache NiFi, and how do you use them to move and transform data between systems?
14. Can you advise how to operate a distributed database system, such as a sharded or replicated database?
15. Can you mention your experience using a DaaS (Database as a service) in any of your projects? If yes, what was the reason for choosing it?
16. How do you store tenants’ data in a SaaS-based application? Do you use a separate schema for each tenant or the same DB schema for all tenants? OR some other strategy?
Microservices
1. Do you agree that a monolith architecture should be the default application architecture instead of micro services architecture?
2. What is your practical experience with some patterns for designing a microservices architecture, such as API gateways, service discovery, and event-driven communication?
3. How do you deploy and manage micro services in a production environment? What guidelines would you suggest to a junior developer in this regard?
4. What is the role of containers in deploying microservices? How do you decide the number of micro services to be deployed per container?
5. How do micro services discover and communicate with each other? What tools and mechanisms have you employed in your projects for discovery and communication between different micro services?
6. How do you test and ensure the quality of microservices in a production environment?
7. Can you describe the difference between unit testing and integration testing, and which of these is suitable for testing microservices?
8. Do you have experience with testing tools for micro services, such as Pact and Spring Cloud Contract, and how do you use them to ensure compatibility between services?
9. What are some common security patterns for micro services, such as token-based authentication and OAuth2?
10. What is the difference between application-level monitoring and infrastructure-level monitoring? Which one is more appropriate for microservices?
Containerization
1. How can containerized applications get deployed in a production environment? Can you describe the best practices you follow?
2. What is the difference between a container image and a container instance, and how are they utilized in containerization?
3. When should Kubernetes or other container orchestration tools be used?
4. Have you worked with cloud-managed Kubernetes services such as Amazon AKS or Azure Kubernetes service?
5. How do containers communicate with one another and the external environment?
6. What is the difference between container networking modes, such as bridge and host modes, and how do you determine which one to choose for a particular system?
7. How do you use typical container networking solutions, such as flannel and Calico, to handle container networking?
8. How do you secure containerized applications in a production environment, and what are some best practices for doing so?
9. What are some common container security patterns, such as container image scanning and container hardening, and how do you use them to improve container security?
10. How do you monitor and log application container behavior in a production environment, and what best practices have you implemented?
11. What is a 12-factor application? Can you identify some of the factors?
12. How is data stored in a containerized application, and what best practices do you follow for managing the container state?
13. What is the difference between a volume and a bind mount, and when should each be used for container storage?
14. What is a container registry, such as Amazon ECR, and what best practices do you use for naming and storing container images?
15. What is the difference between docker compose and dockerfile? Which ones have you used in your projects?
Security
1. What is the difference between SDLS and secure SDLC?
2. What is CORS (Cross-origin resource sharing)? Can you provide an example of where you handled the CORS?
3. What is CSRF (Cross site request forgery)? Can you provide an example of where you handled the CSRF?
4. Can you explain how SSL works?
5. What is the difference between authentication and authorization, and how have you implemented them in your applications?
6. What are some common authentication patterns, such as multi-factor authentication and OAuth2, and how do you use them to improve security?
7. How do you secure the cloud-based network infrastructure of a web application, and what are some guidelines that you follow?
8. What is the difference between SSL and TLS? How do you force TLS 1.3 for your application?
9. Have you performed pen testing or vulnerability scan in your projects? If yes, kindly provide details.
10. What is the difference between a web firewall and an IPS (intrusion prevention system)?
11. What are the best practices for securing a database you have deployed in the cloud?
Cloud Technology
1. What are some common cloud service models, such as Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS), and which ones have you used in your projects?
2. When should you prefer a PaaS (AWS elastic beanstalk or Azure app service) instead of managing the application platform yourself?
3. Can you provide any example of any application using a hybrid cloud?
4. What is Infrastructure as Service (IaC), and what is its role in infrastructure automation?
5. How do you secure your virtual machines deployed in the cloud? Kindly provide some best practices that you have followed.
6. Kindly provide details on how you deployed your containerized web applications in the cloud? Which cloud service did you use and why?
7. What are some common cloud security patterns, such as data encryption and identity and access management (IAM), and which ones have you used in your projects?
8. How do you monitor the health and performance of applications and infrastructure in a cloud environment, and what are some best practices for doing so?
Coding Challenge for Experienced Developers
Here is a coding challenge aiming to evaluate experienced developers. The aim of this coding challenge is to cover all the technical aspects mentioned at the start of this article.
Challenge Description
Develop a social networking web application that allows users to connect with each other, post updates, and share images and videos. The application should consist of the following features:
User authentication
Users should be able to create accounts, log in, and log out. Users should be able to update their profile information and profile pictures.
Social networking
Users should be able to connect with other users by sending connection requests. Users should be able to see the updates posted by their connections.
Update creation
Authenticated users should be able to create updates, which can include text, images, and/or videos. Updates can be public or private to specific connections.
Update viewing
All users should be able to view updates posted by themselves, their connections, or by users that they follow.
Searching and filtering
Users should be able to search for updates based on keywords, and filter updates based on specific users, time ranges, and content type (text, image, video).
Content editing
Authenticated users should be able to edit their own updates, and delete their own updates or comments on updates.
Real-time updates
The application should support real-time updates using websockets, so users can see updates as they are posted.
Mobile support
The application should have a mobile-friendly design that is optimized for smaller screens and touch-based interaction.
Technical Requirements
Develop the web app using any programming language or framework. Scalability, maintainability and efficiency should guide application design. Ideally, the architecture should be based on microservices, however, a monolith will also work fine. Use JUnit or PyTest to write automated tests and XDebug or GDB to troubleshoot errors. Extra marks for caching and database indexing.
Secure the application and follow best practices for authentication, authorization and data protection. Protect against SQL injection and cross-site scripting. You should understand web sockets and be able to create real-time updates using Socket.io or SignalR. Extra marks if you develop a mobile responsive web application.
Submission Instructions
Create a GitHub repository containing your code and any necessary documentation or instructions. Extra marks if you briefly explain your design choices and technical approach.
Conclusion
Assessing the technical skills of experienced developers is crucial for building a successful tech team, but it can be a challenging. In this article, we explored the best practices for evaluating the technical skills of experienced developers, including the key areas to assess and technical questions to ask. By focusing on areas such as programming languages, data structures and algorithms, design and architecture, databases, microservices, containerization, web security and cloud technologies, you can effectively evaluate the skills of experienced developers. We also presented a coding challenge especially designed to assess the skills of experienced developers. That, along with the interview questions, should suffice to gauge the technical abilities of a senior developer.
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