10 Serverless Engineer Interview Questions and Answers for backend engineers

flat art illustration of a backend engineer

1. Can you tell us about your experience with serverless computing?

My experience with serverless computing has been extensive. In my previous role as a Senior Software Engineer at XYZ Company, I was responsible for leading the migration of our monolithic application to a serverless architecture. This involved breaking down our application into smaller, independent services that could be run as serverless functions on AWS Lambda.

As a result of this migration, we were able to significantly reduce our infrastructure costs, as we only paid for the exact amount of compute time we needed. In addition, our application became much more scalable, as we could spin up new instances of our serverless functions to handle increased loads.

  1. Implemented AWS Lambda functions to process data from Kinesis Data Streams, reducing processing time by 50%.
  2. Developed a serverless application architecture for a client that reduced their infrastructure costs by 70%.
  3. Integrated AWS Lambda functions with Amazon S3 to automatically resize images, reducing manual image processing time by 80%.

Overall, my experience with serverless computing has allowed me to create more efficient and scalable applications while also reducing infrastructure costs for my clients. I am excited to continue working with this technology and exploring new ways to optimize its use.

2. What are some benefits of using a serverless architecture?

Serverless architecture offers several benefits, such as:

  1. Cost Efficiency: With serverless computing, you only pay for the exact amount of computing resources and time that you use, which can result in significant cost savings. For example, a company that switched to serverless architecture reduced their cloud costs by 70%.
  2. Scalability: Serverless architectures can automatically scale to accommodate sudden traffic spikes or an increased workload, without the need for manual intervention. This is especially useful for businesses with fluctuating traffic, allowing them to scale up or down as needed. One company saw their website go from 300 visits a month to over 100,000 visits a month with no additional infrastructure costs.
  3. Reduced Complexity: Serverless architecture eliminates the need for infrastructure management, allowing developers to focus on writing code instead of managing servers. This can result in faster application development and deployment cycles.
  4. Improved Resource Utilization: Since serverless architectures are event-driven, resources are only utilized when they are needed, making more efficient use of computing resources. This means that overall performance can be improved, and systems can be built more robustly.
  5. Better Fault Tolerance: Serverless architectures are designed to be highly available and fault-tolerant, which can help prevent outages and minimize downtime. For example, one company saw their uptime increase from 99% to 99.99% after switching to serverless architecture.

3. How do you handle security and compliance in a serverless environment?

One of the most important considerations for any serverless deployment is security and compliance. In order to ensure that our application meets the highest standards of security, we implement a number of best practices and technologies.

  1. Use access control policies: We implement access control policies that ensure the right people have access to the right resources, and that unauthorized access attempts are blocked.
  2. Implement encryption: All data in transit is encrypted using SSL, and all sensitive data at rest is encrypted using AES256 encryption.
  3. Implement IAM Roles: AWS IAM Roles are used to grant permissions to AWS services or AWS resources in a secure way.
  4. Monitor logs: We regularly review logs from all services to identify and analyze any security events or suspicious activity.
  5. Penetration Testing: We regularly perform penetration testing on our application to ensure that there are no vulnerabilities that can be exploited by attackers.
  6. Security Automation: We use security automation tools to scan and identify vulnerabilities in our deployed code. This ensures that security parameters are not being compromised due to development bugs or runtime attacks.
  7. Compliance: We ensure that our application meets all industry-specific compliance requirements by implementing appropriate monitoring, auditing, and reporting tools. We are also certified for compliance with common standards such as SOC2 and ISO27001.

We believe that by following these practices, our serverless environment is highly secure and meets all necessary compliance requirements.

4. What are some common challenges you've encountered when working with serverless technology?

One common challenge I've encountered when working with serverless technology is managing and debugging distributed systems. With traditional monolithic applications, it's easier to locate errors and debug them. However, with serverless architecture, functions are spread across different services and it's challenging to identify the root cause of a problem.

Another challenge I've faced is vendor lock-in. Serverless platforms have their own unique offerings and services, which can make it difficult to migrate to another vendor. This can limit flexibility and increase costs in the long run.

Thirdly, cold starts can be a significant issue when working with serverless technology. When functions are not frequently used, they may need to be restarted, causing a delay in processing time. Cold starts can affect the user experience and performance of the application.

To address these challenges, I have leveraged tools like AWS X-Ray to better trace and debug distributed applications. Additionally, I have worked to containerize applications, giving more flexibility to migrate across vendors. Lastly, I have utilized pre-warming and caching techniques to reduce cold start times, ensuring a better user experience.

5. What are some strategies you use to optimize serverless performance?

One strategy I use to optimize serverless performance is cold-start reduction. The concept of cold-starts refers to the initial boot-up time that occurs when a new function is deployed. This can lead to significant delays in response time, particularly for smaller functions. To combat this, I work to keep the functions warm by implementing a scheduling solution that triggers a small amount of requests every few minutes. This ensures that the functions are always active, which reduces boot time and improves overall performance.

  1. Another strategy I utilize is to minimize code size. This involves eliminating unnecessary dependencies and ensuring that code is written in the most efficient and lightweight manner possible. Not only does this improve performance, but it also helps reduce costs by reducing the amount of compute resources required to run the function.
  2. Additionally, I make sure to properly configure memory and CPU allocation for each function. By analyzing usage patterns and trends, I can determine the optimal memory and CPU configuration tailored to each function's specific needs. This helps to avoid overprovisioning and subsequently, overspending.
  3. Lastly, I conduct regular performance monitoring and testing to identify any bottlenecks or areas for improvement. This involves setting up alerts and automated tests to ensure that any issues can be addressed as soon as they arise. With these strategies in place, I have been able to achieve impressive results, such as a 50% reduction in cold-start times and a 25% decrease in overall compute costs.

6. Can you explain how you would design a serverless application from scratch?

Designing a serverless application from scratch requires a clear understanding of the application requirements and the cloud infrastructure being used. Here are the steps I would follow:

  1. Define the application requirements: Thoroughly understand what the application needs to do, how users will interact with it, and the expected usage patterns. This will help in determining the best cloud services to use.

  2. Select the services: Based on the requirements, select the necessary AWS services for different components of the application, such as API Gateway, Lambda, DynamoDB, S3, etc. This will involve a trade-off between cost, scalability, performance, and ease of management.

  3. Design the data model: Create a database schema for DynamoDB, and determine how data will be partitioned, how indexing will be used, and how consistency will be maintained.

  4. Develop the application logic: Write functions in Node.js and configure them in AWS Lambda. The functions will use the appropriate AWS SDKs to access other AWS services and interact with the database created in DynamoDB. Cold start times of lambda functions will be managed in order to reduce latency and improve performance.

  5. Configure API Gateway: Create RESTful APIs using API Gateway, and map them to the Lambda functions. Configure authentication and authorization for the APIs as needed.

  6. Test and deploy: Test the application thoroughly in different environments (dev, stage, prod) to ensure it meets the requirements. Deploy the application and all necessary resources into the production environment.

  7. Monitor and scale: Set up monitoring for the application, and configure automatic scaling rules for the AWS services used. Monitor for any application performance issues, and troubleshoot as needed.

Following these steps will ensure that the serverless application is well-architected, scalable, and secure. Last year, I used this approach to design and build a serverless chatbot application for a banking client. The application was accessed by over 10,000 users per day, with a response time of less than 1 second, and incurred a cost of less than $100 per month.

7. How do you handle scalability in a serverless environment?


As a serverless engineer, I understand that scalability is an important factor while working with serverless architecture. Below are a few steps that I take to handle scalability:

  1. Auto-scaling: In a serverless environment, auto-scaling is a key feature that helps to handle scalability. I ensure that my serverless functions are designed to auto-scale based on the incoming traffic. This helps in ensuring that the application is always available to the users without any downtime or lagging.
  2. Optimizing the Function: I make sure that the serverless functions are optimized for performance. I analyze the function's code to identify any bottlenecks that can impact the performance. This helps in ensuring that the function can handle the increased load efficiently and without performing slower.
  3. Using Caching: I use caching techniques to reduce the latency and increase the response time of the serverless application. By using caching, I ensure that the frequently accessed data is stored in the cache and is available for immediate access without having to hit a database or external resource.
  4. Load Testing: I regularly perform load tests on the serverless applications to determine their scalability limits. This helps in identifying any potential bottlenecks and scaling limits that the application has, thus allowing me to take necessary actions.

By following these steps, I have successfully handled scalability issues for several projects. For instance, while working on a project for an e-commerce website, we were able to handle a traffic spike of 5000 requests per second during a sale event without any downtime or lagging.

8. What strategies do you use to monitor and troubleshoot serverless applications?

As a serverless engineer, one of the key strategies I use to monitor and troubleshoot serverless applications is through a combination of leveraging monitoring tools and incorporating thorough logging.

  1. I start by implementing monitoring tools such as AWS CloudWatch and Datadog to track function executions, monitor system metrics, and identify trends over time. With this data, I can quickly pinpoint any errors or slowdowns that may be impacting the overall performance of the application.
  2. Additionally, I incorporate thorough logging by capturing data points such as error messages, function execution times, and payload data. By analyzing logs, I can gain valuable insight into the behavior of the application and uncover potential issues before they escalate.
  3. When troubleshooting, I leverage automated testing to ensure that code is thoroughly vetted before it is deployed to production. This includes running unit tests, integration testing, and load testing to validate that the application is performing as expected and is highly available.
  4. Finally, I maintain clear communications with stakeholders and team members to ensure that any issues are quickly addressed and resolved. Through regular communications and coordination, we can proactively address any issues and avoid potential downtime and system failures.

Through this approach, I have successfully managed and maintained highly available and performant applications, reducing downtime and improving overall system stability by over 95%.

9. Can you tell us about a particularly challenging serverless project you've worked on and how you overcame any obstacles?

During my time at XYZ Company, I worked on a serverless project that aimed to migrate the company's data analytics platform to a serverless architecture on AWS. The project was challenging because it involved managing and processing large volumes of data in near real-time.

  1. The first obstacle we faced was designing an efficient data pipeline to move data from different sources to the serverless analytics platform. I overcame this challenge by leveraging AWS Lambda functions to ingest and process the data in parallel, which significantly reduced the pipeline's processing time.
  2. The second challenge was optimizing the platform's performance and scalability. We overcame this obstacle by leveraging AWS DynamoDB to store metadata and AWS Aurora Serverless for the database. This architecture allowed the platform to scale to handle a high volume of requests without any performance issues.
  3. Lastly, we had to create a robust monitoring and alerting system to detect and notify us of any potential issues with the platform. I overcame this challenge by implementing AWS CloudWatch and SNS to monitor the platform's performance and send alerts in case of any anomalies.

Thanks to these solutions, our serverless analytics platform became more efficient, scalable and reliable, with faster processing times, reduced costs, and a better user experience, as evidenced by a 30% increase in user engagement and a 50% reduction in error rates.

10. What do you see as the future of serverless computing and how do you keep up with new developments in the industry?

Serverless computing has become a dominant trend in the technology industry, and I see it continuing to grow and evolve in the future. I believe that serverless computing will play a significant role in the next-generation applications and software solutions.

To stay up-to-date with the latest developments in the industry, I actively participate in online communities and forums. I also attend conferences and meetups to network with other professionals and hear about the latest technologies and solutions.

One example of my ability to keep up with developments in serverless computing is my experience with AWS Lambda. In a recent project, I was able to reduce our infrastructure costs by 50% by using AWS Lambda functions to replace our server infrastructure. This allowed us to save resources and time, while improving our overall performance and scalability.

  1. I follow industry leaders and experts on social media platforms such as Twitter and LinkedIn. This helps me stay informed of new developments in serverless computing and related fields.
  2. I also attend webinars and online courses to learn about new tools and techniques.
  3. As a lifelong learner, I am always seeking to add new skills and knowledge to my toolkit.

Overall, I believe that serverless computing is the future of cloud computing, and I am excited to be a part of this rapidly evolving field.


Congratulations on preparing for your serverless engineer interviews! As you move forward in your job search, don't forget to write a compelling cover letter that highlights your skills and experiences. Take a look at our guide on writing a standout cover letter to set you apart from other candidates. Another important step is to prepare an impressive CV that showcases your skills and experience in the best possible way. Check out our guide on writing an appealing resume for backend engineers to create a powerful CV that catches the attention of potential employers. If you're actively looking for new opportunities, explore our remote backend engineer job board to find your dream job. We regularly update our job listings, so keep checking back to find your perfect match. Best of luck with your serverless engineer interviews and your future job search!

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