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Mid / Senior Backend NodeJS Technical Interview | Application to Offer Part 2/2



Backend Team Lead @ vivoo

Before entering technical interviews for the Mid/Senior Backend Node.js Developer or similar Backend positions, there are several things to consider. In the following, I will provide a detailed explanation of key aspects and pay to attention points.

Here, instead of interviews for online coding assestments or algorithms, which are the pre-qualification, I explained the important points about the skillset required to pass the interviews in companies that conduct interviews in the form of framework/concept/project hand-on-experience and get official offers.

Part 1 Read from click here:

In-depth knowledge of Node.js: As a Senior Backend Node.js Developer, you are expected to have a strong command of Node.js. Make sure you have a deep understanding of the Node.js runtime, event-driven architecture, and asynchronous programming concepts. Familiarize yourself with the core modules, package management (NPM/Yarn), and popular frameworks such as Express.js, Koa.js, or Nest.js. Nest is highly popular nowadays 🚀

Here is the backend key concepts:#

  1. JavaScript proficiency: Since Node.js is built on JavaScript, it is crucial to have a solid understanding of the language. Be well-versed in modern JavaScript features, object-oriented programming principles, and functional programming concepts. Ensure you are familiar with ES6+ syntax, closures, promises, and async/await.

  2. Web technologies and protocols: As a backend developer, you will interact with various web technologies and protocols. Gain knowledge of RESTful APIs and their design principles, HTTP/HTTPS protocols, status codes, headers, and request/response mechanisms. Understand how to handle cookies, sessions, and implement authentication and authorization mechanisms such as JWT. Besides, information on basic network communication such as port forwarding, load balancing, proxy will be great.

  3. Data storage and databases: Backend developers often work with databases. Gain proficiency in database concepts and technologies, particularly related to Node.js. Understand different database types (relational and NoSQL), query languages (SQL, MongoDB query language), and database modeling. Knowledge of ORMs (e.g., Sequelize, TypeORM) or ODMs (e.g., Mongoose) is also valuable.

  4. Testing and debugging skills: Employers value developers who can write clean and bug-free code. Familiarize yourself with various testing methodologies, such as unit testing, integration testing, and end-to-end testing. Learn popular testing frameworks like Mocha, Jest, or Chai, and understand how to use tools like Postman or Insomnia for API testing. Showcase your ability to write effective test cases and debug issues efficiently.

  5. Performance optimization: Backend developers need to optimize application performance. Understand how to profile and identify performance bottlenecks in Node.js applications. Learn techniques for code optimization, caching, and database query optimization. Familiarize yourself with tools like pm2, prometheus etc. for performance monitoring and load testing( or similar tools great).

  6. Security best practices: Security is a critical aspect of backend development. Gain knowledge of common security vulnerabilities, such as cross-site scripting (XSS), SQL injection, and cross-site request forgery (CSRF). Learn best practices for securing APIs, implementing encryption, and handling user authentication and authorization securely. Stay updated with the latest security trends and vulnerabilities. Authentication systems and OAuth mechanism basics should at least be known theoretically

  7. Scalability and concurrency: Backend systems often face scalability and concurrency challenges. Demonstrate your understanding of techniques for scaling Node.js applications, such as load balancing, horizontal scaling, and caching. Understand how to manage concurrent requests, handle race conditions, and use asynchronous patterns effectively. This is a deep subject that includes many design techniques. Many components need to be looked at one by one. Architecture, database, queue structures etc.

  8. Messaging Queue Systems: Firstly, these systems enable scalable and resilient architectures by decoupling components and promoting asynchronous communication. They facilitate loose coupling and microservices, allowing for independent evolution of services. Messaging queues ensure message order and reliability, crucial for scenarios like financial transactions. Integration capabilities enable communication with external services and multiple channels. Lastly, systems like RabbitMQ and Kafka excel at handling real-time data streams, enabling event sourcing, log processing, and real-time analytics. Understanding and using these messaging queue systems showcases expertise in building scalable, resilient, and data-intensive backend systems, making senior backend developers highly valuable in job interviews. If you work with one of these “AWS SQS, SNS, RabbitMQ, and Kafka” it would be great.ü

  9. Scheduled & Cron Jobs: These systems enable the automation of recurring tasks and scheduled operations, such as data backups, data synchronization, and periodic data processing. By leveraging cronjob and scheduled job systems, developers can ensure the timely execution of these tasks, improving efficiency and reducing manual effort. Understanding these systems also demonstrates proficiency in optimizing workflows, maintaining critical backend operations, and implementing efficient background processes. Having experience with cronjob and scheduled job systems showcases a developer’s ability to design and manage reliable, automated systems, making them valuable candidates during job interviews. I can suggest to take a look & hands on experince on linux’s cron, Redis cron system

  10. Version control systems: Proficiency in version control is crucial for collaborative software development. Familiarize yourself with Git, including common Git commands and workflows. Understand concepts such as branching, merging, rebasing, and resolving conflicts. Showcase your ability to work with remote repositories, use branching strategies effectively, and collaborate with other developers.

  11. Real-world project experience: Prior experience working on real-world projects is highly valuable. Highlight your previous projects, emphasizing your contributions, responsibilities, and outcomes. Discuss challenges you faced and how you overcame them. Provide examples of project-specific achievements, such as optimizing performance, improving scalability, or implementing robust security measures.

  12. Stay updated with industry trends: The tech industry is constantly evolving, and staying updated is essential. Keep abreast of the latest trends, frameworks, libraries, and tools relevant to Node.js development. Follow reputable websites, blogs, and forums, and participate in relevant communities and online discussions. Employers appreciate candidates who show enthusiasm for continuous learning. Practice coding challenges and system design: Technical interviews often include coding challenges and system design questions. Practice solving coding problems using platforms like LeetCode, HackerRank etc.

Additionally, study system design principles and practice designing scalable and efficient architectures for real-world scenarios. Those on the application side are like this, you need to know a little bit about devops. Although you write a backend, you can better understand where to put the parts while designing the system, with the logic of devops, to understand which layer comes out in case of containerization or a problem. At the same time, if an approach suitable for continuity and agile manifesto is desired, DevOps practices offer great mindsets for this continuity. These concepts may be a bit extreme for a mid-level backend developer. However, in many places where modern technologies are used, these concepts now form the basis of infrastructures.

These areas play crucial roles in modern application development and deployment.

DevOps Mindset:#

DevOps focuses on bridging the gap between development and operations teams, ensuring efficient collaboration and streamlining the software delivery process. Familiarize yourself with DevOps principles, tools, and practices, including:

  • Continuous Integration and Continuous Deployment (CI/CD): Understand CI/CD pipelines, which involve automating the building, testing, and deployment of software. Learn popular CI/CD tools like Jenkins, Travis CI, or GitLab CI/CD.
  • Infrastructure as Code (IaC): Gain theoretical knowledge of provisioning and managing infrastructure using code. Learn basic concepts about tools such as Terraform or AWS CloudFormation to define and deploy infrastructure resources.
  • Monitoring and Logging: Learn about monitoring tools (e.g., Prometheus) and logging solutions (e.g., ELK Stack) to ensure proper observability and troubleshoot issues effectively.

Docker(Containerization Concepts):#

Docker is a popular containerization platform that allows developers to package applications and their dependencies into isolated containers. Understanding Docker is crucial for efficient application deployment and scalability. Consider the following aspects:

  1. Docker Compose: Understand how to define and manage multi-container applications using Docker Compose, including services, networks, and volumes.
  2. Container Orchestration: Gain knowledge of container orchestration platforms like Kubernetes, which provide advanced features for managing containerized applications at scale.


Kubernetes is a container orchestration platform that automates the deployment, scaling, and management of containerized applications. Proficiency in Kubernetes is highly valuable, especially for deploying and scaling Node.js applications. Consider the following areas:

  1. Kubernetes Architecture: Understand the components of a Kubernetes cluster, such as nodes, pods, services, and deployments.
  2. Deployment Strategies: Learn about different deployment strategies, including rolling updates, blue-green deployments, and canary releases.
  3. Scaling and Load Balancing: Gain knowledge of scaling applications horizontally and configuring load balancers within a Kubernetes cluster.
  4. Monitoring and Autoscaling: Familiarize yourself with Kubernetes-native monitoring tools like Prometheus and Grafana. Understand how to configure autoscaling based on metrics like CPU utilization or custom metrics.

### Conclusion / Summary In conclusion, the technical interview process for mid/senior backend developers can be challenging, but it is important to be prepared and to practice your skills. Even if you do not know everything in depth, knowing the logic of work, small experiences in similar situations make the person stand out in such interviews. This information is very important for general positions, not for positions that belong to areas that are known in depth.

By following the tips in this article, you can increase your chances of success and land your dream job.

Feel free to contact with me!