10 API gateway and proxy management Interview Questions and Answers for api engineers

flat art illustration of a api engineer

1. What experience do you have with API gateway and proxy management?

During my previous role at XYZ company, I was responsible for managing the API gateway and proxy for our e-commerce platform. I successfully implemented a new gateway that improved response times by 30% and decreased error rates by 20%.

  1. I have experience setting up client authentication and authorization using OAuth and API key. I implemented a new OAuth flow that allowed our clients to request access tokens through a self-service portal, reducing the burden on our support team.
  2. I have worked extensively with rate limiting and throttling to prevent abuse and ensure service availability. I implemented a dynamic rate limiting strategy that adjusted thresholds based on usage patterns, resulting in improved system stability and reliability.
  3. I am familiar with implementing SSL termination and applying security measures to protect API endpoints from unauthorized access. I implemented SSL termination using AWS Certificate Manager, and set up IP whitelisting to limit access to our internal services.
  4. I have experience monitoring API traffic and performance using tools like Datadog and Prometheus. I set up custom dashboards to track key metrics like response times, error rates, and request volumes, allowing us to proactively identify issues and optimize performance.
  5. I have also worked with legacy APIs that required translation and transformation before being sent to downstream services. I implemented a custom translation layer that transformed XML messages into JSON, and vice versa, resulting in improved compatibility and reduced latency.

Overall, my experience with API gateway and proxy management has allowed me to develop a deep understanding of how to optimize and secure API traffic, while providing a seamless experience to clients and users.

2. What kind of APIs have you worked with in the past?

Sample Answer:

  1. I have worked with RESTful APIs extensively in my previous role as a software engineer at ABC Inc. I was responsible for building and maintaining the company's API infrastructure to support their mobile and web applications. Through my work, I was able to improve API response time by 40% and decrease server errors by 50%.
  2. In addition to RESTful APIs, I also have experience with SOAP APIs. At XYZ Corp, I was part of a team that integrated a third-party SOAP API into the company's software stack. As a result, our software was able to seamlessly interact with the third-party software, reducing response time by 20%, which led to increased customer satisfaction.
  3. Furthermore, I have also worked with GraphQL APIs. At DEF Corp, I led the development of a GraphQL API for their new mobile application. The implementation of the GraphQL API drastically improved the application's performance, resulting in a 25% increase in user engagement and time spent on the app.
  4. In my personal projects, I have experimented with gRPC APIs. I built a simple chat application using gRPC APIs, which allowed for real-time messaging between users. The use of gRPC APIs improved the app's scalability, as it was able to handle a large volume of simultaneous connections without any performance degradation.
  5. Overall, my experience with various types of APIs has given me a strong foundation in API development and management.

3. How do you handle authentication and authorization in your API gateway configurations?

Authentication and authorization are critical components of any API gateway configuration. My approach is to use a combination of authentication and authorization mechanisms to ensure secure access to APIs.

  1. First, I use API keys to authenticate users. API keys are unique identifiers that are assigned to each user, and they are used to authenticate users when they access the API via the gateway. This ensures that only authorized users can access the API.
  2. Next, I use OAuth2 to handle authorization. With OAuth2, users are granted access to specific resources based on their authorization levels. This is done using access tokens, which are issued to users once their authorization levels have been verified. These tokens are then passed to the API gateway along with the API key to ensure that only authorized users can access the API.
  3. Finally, I also employ rate limiting to ensure that the API is not overwhelmed with requests. I use a combination of IP-based throttling and user-based throttling to ensure that users can only make a certain number of requests per second. This helps prevent denial of service attacks and ensures that the API remains responsive.

The result of this approach is a highly secure API gateway configuration that ensures only authorized users can access the API. It also helps prevent overload that can lead to system crashes or unresponsiveness, ensuring that the API remains reliable and available for use.

4. What steps do you take to ensure the security of the API gateway and the APIs it manages?

What steps do you take to ensure the security of the API gateway and the APIs it manages?

Firstly, our team designs secure APIs by following the best practices related to input validation, SSL/TLS certificate authentication, and encryption. After designing, we perform dynamic security testing of APIs to detect security vulnerabilities.

Then, we implement the security mechanisms like API keys, OAuth2.0, and other authentication protocols to control access to critical API resources. These authentication mechanisms limit the scope of API access to the authorized entities like internal services, applications, or third-party vendors.

We monitor API traffic and behavior using robust security tools for continuous security threat detection and reporting. We have implemented tools like API-traffic analyzing tools and API threat detectors to monitor unusual API requests, unusual geographic zones, and abnormal API performance. We also use Intrusion detection and prevention systems and firewalls to provide seamless protection against malicious bots and cyber attacks.

Regarding compliance, we ensure that our APIs respect all confidentiality and data protection schemes such as General Data Protection Regulations (GDPR), PCI-DSS, Health Insurance Portability and Accountability Act (HIPAA), and others, depending on the industry which the API supports.

Finally, we also ensure that API documentation contains specific and clear instructions on secure coding practices and vulnerabilities to avoid for the internal API developers and third-party developers who intend to use the APIs.

5. What methods do you use for monitoring and performance tuning your API gateway?

As an experienced API gateway and proxy management professional, I understand the importance of monitoring and optimizing the performance of API gateway to ensure minimal downtime and efficient delivery of services. I use the following methods for monitoring and performance tuning:

  1. Logging and Analysis: I use logging for all requests and responses passing through the API gateway. I keep track of the response time, error rates, and authentication failures to detect performance issues. I analyze the logs regularly to detect and solve any slow or faulty operations.
  2. Caching: I implement caching for frequently requested data, which reduces the load on the backend and improves response times. I also use a distributed caching system to reduce latency and improve scalability.
  3. Load Testing: I perform load tests on the API gateway to simulate high user traffic and peak loads. This helps me identify performance bottlenecks and tune the API gateway for optimal performance. For example, in my previous role, I conducted a load test using JMeter, and we managed to reduce the response time from 5 seconds to 1 second.
  4. Auto Scaling: I use auto-scaling to add more computing power to the API gateway during peak demand. This helps me ensure that there is always enough capacity to handle the traffic to avoid downtime or degradation in performance. For example, in my previous role, I configured the AWS API Gateway to scale according to demand, and this helped us handle a sudden surge in traffic without any issues.
  5. Security: I ensure that the API gateway is secure by using authentication, encryption, and access controls. This enhances the performance of the API gateway by reducing the risk of unauthorized access, data breaches, and Denial of Service (DoS) attacks.

These methods have proven effective in monitoring and performance tuning API gateways. In my previous role, I managed to maintain an uptime of 99.99% and reduce the average response time from 2 seconds to 500ms.

6. How do you implement rate limiting and other traffic management policies in your API gateway?

Implementing rate limiting and other traffic management policies is essential for preventing overloading and unexpected behavior in your API. Here's an example of how I have done this:

  1. First, I configure a rate-limiting policy that restricts the number of API requests from a particular IP address within a specified time period. This prevents a single client from monopolizing system resources and ensures fair use for all clients.

  2. Next, I set up circuit breaker policies to handle failures in the upstream services. This effectively stops the cascading failure that caused a slow response time or completely broke down the service.

  3. Finally, I configure an API key policy to track and limit usage on all API endpoints. This policy requires the client to identify itself through a unique API key that is automatically generated based on their credentials. If the client exceeds their allowance, they will receive a 403, essentially blocking further API requests for a specified period.

I've seen significant benefits implementing these policies. Our API gateway achieved a 100% improvement in response time and a 50% reduction in error rates due to service failures. We also saw a 200% increase in the number of monthly active users, as we were able to provide more significant resources with the stable performance that these policies offer.

7. Can you walk me through a particularly challenging API management project you've worked on?

One of the most challenging API management projects I've worked on was for a large e-commerce company. The company had over 50 different APIs that were being used by various internal applications, as well as external partners.

  1. First, we conducted a thorough audit of all the APIs to identify any issues or potential security vulnerabilities.
  2. Next, we created a centralized API gateway to manage all the APIs in one place. This allowed us to streamline the management of the APIs, as well as enforce consistent security policies across all the APIs.
  3. We worked closely with the various internal teams to migrate all their applications to use the new centralized gateway.
  4. We also implemented rate limiting and throttling policies to prevent any one application or partner from overwhelming the system.
  5. To further improve security, we implemented a robust authentication and authorization system using OAuth 2.0.
  6. Finally, we set up comprehensive monitoring and logging to quickly identify any issues or errors.

The results of this project were incredible. We were able to significantly improve the security and overall performance of the company's APIs. In addition, the centralized gateway made it much easier to manage and update the APIs, which resulted in faster turnaround times for updates and new features. The rate limiting and throttling policies led to more stable and reliable results for all internal and external users of the APIs. And the monitoring and logging systems we put in place allowed us to quickly identify and resolve any issues, resulting in minimal downtime for the APIs.

8. What's your approach to resolving issues with API routing and integration?

My approach to resolving issues with API routing and integration includes the following steps:

  1. Identifying the root cause of the issue by analyzing the system logs, monitoring tools, and API documentation.
  2. Collaborating with the development team to find out if the issue is related to programming flaws, infrastructure issues, or if it's a communication problem between microservices.
  3. Testing the API endpoints using Postman or any other testing tool to ensure they are working correctly.
  4. Performing load testing to determine if there are any performance bottlenecks.
  5. Troubleshooting security-related issues by analyzing the security configuration of the API gateway and proxy servers.
  6. Implementing the necessary changes in the API gateway and proxy management systems, including creating new routes or modifying existing ones.
  7. Deploying the changes to the production environment after appropriate testing in development and staging environments.
  8. Continuously monitoring the system after deployment to ensure the issue is fully resolved.
  9. Documenting the resolution process, including status updates, to ensure future developers can use this as a reference.
  10. Evaluating the effectiveness of the resolution process to determine if improvements can be made.

By following these steps, I was able to resolve an issue with API routing that was causing a 10% increase in response times. By working with the development team to identify and implement the necessary changes, we were able to reduce response times by 20%, resulting in a more efficient system for our users.

9. Have you worked with any API gateway vendors or open-source solutions, and if so, which ones?

In my previous role as a software engineer, I have worked extensively on API gateway and proxy management solutions. I have experience using both open-source solutions and vendor solutions. I have worked with vendors like Apigee, AWS API Gateway, and Kong. I have used open-source solutions like Ambassador and Istio.

  1. I have worked with Apigee to create and manage APIs for a large retail client. I was responsible for configuring Apigee policies like rate limits, caching, and security policies. I also worked on the integration of the Apigee platform with the client's existing systems. The project was a success, and the client saw a 25% increase in API traffic within six months.
  2. For another client, I helped set up an AWS API Gateway to manage traffic to their microservices. I worked on configuring the API Gateway to handle authentication and authorization using AWS Cognito, as well as setting up caching policies. I was able to reduce the latency of API calls by up to 50% by using caching effectively.
  3. Using Kong, I have helped implement a self-service API platform for a financial services client. I was responsible for setting up automated deployment pipelines and implementing Kong's rate limiting policies. This resulted in a significant reduction in the time it took to deploy new APIs and an increase in customer satisfaction.
  4. With Istio, I have worked on implementing traffic management policies for a telecommunications client. I was responsible for creating virtual services and destination rules to manage traffic to their microservices. The project was successful, and the client reported a 30% reduction in latency for API calls.

Overall, I have found that both vendor solutions and open-source solutions have their strengths and weaknesses. The choice of solution depends on the client's specific requirements and budget. However, regardless of the solution used, proper configuration and management of API gateways and proxies is crucial for the success of any API project.

10. How do you stay up to date on the latest trends and technologies in API gateway and proxy management?

As an API gateway and proxy management expert, it's crucial to stay up to date on the latest trends and technologies in the field. Here are the strategies that I use:

  1. Networking with peers: I attend industry conferences and join online forums to connect with other professionals in the field. By engaging in conversations, I learn about emerging technologies and best practices from experts.
  2. Following industry blogs: I regularly read blogs from top industry experts and thought leaders, such as Kong, Apigee and AWS, to keep my knowledge up to date. I also follow blogs from relevant tech companies to gain an understanding of their latest developments and how they may impact the API gateway space.
  3. Tech Meetups: I attend technology meetups that cover topics related to API management, gateway or proxies. This is a great opportunity to learn from other professionals who are currently implementing these technologies in their companies, share ideas and get updates on the latest trends.
  4. Learning from online courses: I take online courses on platforms such as Coursera, Udemy and Pluralsight to develop my skills and learn about new API gateway and proxy technologies. These courses are an excellent way to stay up to date on developments in the field
  5. Mentorship: I seek out mentors who have more experience in API gateway and proxy management than myself. Through mentorship, I can learn about best practices, receive feedback and stay up to date on the latest trends and technologies.

Using these strategies, I've been able to stay on top of the latest trends and technologies in API gateway and proxy management. In my current role, I implemented a new API gateway solution that increased our efficiency by 30%, which was only possible through my deep knowledge of the latest industry trends and best practices.


If you made it to the end of this article, congrats! You are on the right track to ace your API gateway and proxy management interview. However, there are a few more steps to take before applying for your dream API engineer job. One important step is writing a captivating cover letter. Check out our guide on writing a cover letter tailored for API engineers to help you stand out from the rest of the applicants. Don't forget to prepare an impressive CV as well. Our guide on writing a resume for API engineers can help you showcase your skills and experience effectively. Finally, use our Remote Rocketship job board to search for remote API engineer jobs. With our job board, finding a remote job has never been easier. Happy job hunting!

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