10 API rate limiting and throttling Interview Questions and Answers for api engineers

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1. What experience do you have in API rate limiting and throttling?

During my previous role as a software developer at XYZ Company, I was responsible for implementing API rate limiting and throttling for a mobile app that had recently launched. We were experiencing a high volume of traffic and needed to ensure that our API was protected from possible malicious attacks or overuse.

  1. First, I conducted research on the best practices for API rate limiting and throttling and identified the different types of limits that could be implemented (such as per user, per IP address, or per endpoint).
  2. Next, I worked with our team to determine the appropriate limits for each endpoint and implemented rate limiting using a token bucket algorithm. This involved ensuring that each request used up some of the tokens in the bucket and that new tokens were generated at a certain rate.
  3. I also implemented throttling by setting limits on the maximum number of requests that could be made within a certain timeframe. This was important to prevent sudden spikes in traffic from overloading our API and causing downtime.
  4. We monitored our API usage using tools such as New Relic and CloudWatch, and made adjustments to our rate limiting and throttling algorithms as needed based on the data we collected. Our efforts paid off – we were able to handle the increased traffic without any major issues.

In the end, our implementation of API rate limiting and throttling resulted in a more secure and reliable API that could handle a high volume of traffic. I have since applied this experience to other projects, including an e-commerce platform that needed to protect against possible DDoS attacks. Through my experience, I have learned the importance of having proper rate limiting and throttling measures in place and how to adapt them to different scenarios.

2. What are the most common issues you have faced while implementing API rate limiting and throttling?

While implementing API rate limiting and throttling, I have faced several common issues. One of these is determining the optimal rate limits for each API endpoint. Determining the correct rate limit involves analyzing data such as request frequency, response times, and user behavior. In the past, I had to experiment with different rate limits for each endpoint in order to find the most effective one. For example, when we set a rate limit of 10 requests per minute for an endpoint, it resulted in an increase in the number of successful requests by 20% compared to when we set it to 5.

Another issue I encountered is balancing the needs of our users with the needs of our API. While we want to allow our users to make as many requests as possible, we also need to prevent overloading our server. I had to find a way to balance these needs with the use of appropriate throttling techniques. By using throttling, we were able to limit the number of requests made by each user and still ensure that we met our service level agreements.

Finally, I have also faced challenges in ensuring that our rate limiting and throttling implementation is scalable. At times we underestimated the demand on a specific endpoint and it would become inadequate quite fast. We tried implementing auto-scaling technology, which automatically adjusts the number of available instances based on traffic or capacity. Switching to this improved horizontal scaling approach allowed us to maintain the effectiveness of our rate limiting and throttle strategy even as traffic to the endpoints increased over time.

  1. Determining optimal rate limits for each API endpoint
  2. Balancing needs of users with the needs of the API
  3. Ensuring implementation is scalable

3. What strategies do you use to monitor and analyze API usage and performance?


At my previous job, we heavily relied on analytics tools to monitor and analyze API usage and performance. We primarily used API monitoring and analytics tools such as New Relic, Datadog and Splunk.

Through these tools, we were able to gather real-time data on API usage, which enabled us to identify bottlenecks, track trends and optimize API efficiency. We also set up alerts to notify us of any unusual spikes in API usage or errors, allowing us to take proactive measures to resolve any issues before they escalated.

We used custom dashboards to visualize this data, making it easier to identify and analyze patterns. For example, we developed a dashboard that showed the number of requests per second, average response time, and the number of concurrent users accessing the API. By tracking these metrics, we were able to identify performance issues and take the necessary steps to optimize the API.

Thanks to these analytics tools, we were able to improve our API performance by over 30%, resulting in a better user experience and increased customer satisfaction.

4. How do you ensure that the API rate limiting and throttling policies are effective and accurate?

As a software engineer, I understand that API rate limiting and throttling policies are crucial for ensuring that our services are secure and reliable. To ensure effectiveness and accuracy of these policies, I follow these steps:

  1. First, I analyze the historical usage data to understand the frequency and typical payload sizes of requests over time. This allows me to set realistic limits that are not too restrictive nor too permissive.
  2. Next, I gather feedback from the users and stakeholders to ensure that the limits are acceptable and align with their expectations.
  3. Then, I test the policies with various scenarios and stress test them to ensure that the system behaves as expected under heavy loads and unexpected circumstances.
  4. I also monitor the system performance and logs to identify any unusual patterns or anomalies that may indicate incorrect rate limiting or throttling.

By rigorously following these steps, I have ensured that the rate limiting and throttling policies I developed for a previous project were successful in preventing over 95% of unauthorized access attempts and significantly reducing server load by up to 70% during peak usage hours.

I am confident that I can apply these principles to ensure that the API rate limiting and throttling policies for your organization are effective and accurate.

5. How do you balance user satisfaction with system performance while implementing rate limiting and throttling policies?

Balancing user satisfaction with system performance is a critical task when applying rate limiting and throttling policies. One way to achieve this balance is by continuously monitoring and analyzing user traffic and system performance data. By analyzing the data, you can identify patterns and trends that can help you optimize the rate limiting and throttling policies to enhance user satisfaction while ensuring system performance remains consistent.

  1. Implementing a flexible rate-limiting policy that is balanced across users can help distribute the load evenly and ensure that no individual user is adversely affected. By setting the rate limits based on user need and usage, we can guarantee that high-volume users are not occupying all the available resources, leaving none for new users.
  2. We can also implement throttling and error handling mechanisms that provide positive feedback to users such as alternative solutions to reduce latency or usage. Providing users with clear and detailed error messages that explain the reasons for the limit can reduce frustration and improve their overall satisfaction.
  3. To ensure system performance, we can also implement caching mechanisms that store frequently requested responses to avoid repeating the same queries that can help reduce latency and improve system performance.

At my previous job, I worked on a project where we implemented a rate-limiting policy to optimize system performance while maintaining user satisfaction. We analyzed the user traffic data and identified that 80% of users were within the allowed limit while the other 20% exceeded the limit consistently. We decided to adjust our rate-limiting policy to provide more flexibility to the users, giving them an extended limit for the first few requests to reduce rejection rates. This led to a 15% increase in user satisfaction and over 30% reduction in rejection rates, improving the overall system performance.

6. What measures do you take to prevent API abuse and exploits while implementing rate limiting and throttling policies?

As a developer, I understand the importance of implementing effective rate limiting and throttling policies to prevent API abuse and exploits.

  1. Firstly, I implement a secure authorization process to ensure that only authorized users can access the API. This includes requiring API keys or OAuth2 tokens for authentication.
  2. Next, I consistently monitor API traffic using tools like Amazon CloudWatch or Datadog. By analyzing traffic patterns, I can detect any unusual or abnormal spikes in traffic that may indicate a potential attack or abuse.
  3. To prevent DDoS attacks, I make use of AWS Shield, a managed DDoS protection service that makes use of global threat intelligence to detect and filter malicious traffic. This ensures that my API servers stay up and running, even in the face of large-scale attacks.
  4. I also set up API rate limits and throttling mechanisms to prevent excessive requests from any single user or IP address. This helps prevent API abuse and ensures a fair use of resources. For example, I might limit the number of requests per minute or per hour, or set up dynamic rate limits that adjust based on traffic patterns.
  5. Finally, I use a Web Application Firewall (WAF) like AWS WAF to protect against attacks like SQL injection, Cross-Site Scripting(XSS) or Cross-Site Request Forgery(CSRF). AWS WAF allows me to create custom rules to block malicious traffic to my API endpoints.

By implementing these measures, I can ensure that my APIs are protected from abuse and exploits, while ensuring high availability for legitimate users. For example, by implementing these measures in an e-commerce site, the API responded only to a maximum of 1000 requests made per minute per IP and potential DDoS attacks were mitigated resulting in a 99.9% uptime for the service.

7. Have you implemented any automated tools to assist in rate limiting and throttling process?

Yes, in my previous role as a software engineer at XYZ Company, I implemented an automated tool to assist in our rate limiting and throttling processes. The tool was designed to monitor API requests and responses, and automatically adjust the rate limits in real time to prevent overloading and ensure the overall performance of the system.

  1. Firstly, I set up an API gateway that intercepted all incoming API requests and forwarded them to the tool for analysis.
  2. Next, I created a custom algorithm in Python to analyze the API request data, including the endpoint, HTTP method, and payload size.
  3. Based on the analysis, the tool would assign a dynamic rate limit to the request. This rate limit would be adjusted constantly in real time, depending on the number of requests being made.
  4. If the rate limit was exceeded, the tool would automatically throttle the rate of incoming API requests until the limit was no longer exceeded, thus preventing overloading and ensuring the stability of the system.
  5. The tool also sent alerts to the developers, notifying them of any errors or issues so that they could take any necessary actions.

As a result of implementing this automated tool, we were able to significantly improve the overall performance of our API system, while reducing the number of manual interventions needed. We observed a 25% decrease in API response times, and a 75% decrease in overall API-related issues reported by our customers.

8. How do you ensure that the API rate limiting and throttling policies meet compliance regulations?

Compliance regulations are crucial when it comes to API rate limiting and throttling policies. It is essential to ensure that the API policies meet regulatory requirements. At my previous company, we developed a compliance framework that combined technical policies with legal and regulatory requirements to ensure that our API rate limiting and throttling policies were compliant.

  1. We actively monitored regulatory changes and incorporated them into our policies.
  2. We made sure that we had a clear understanding of the regulations and the impact on our policies.
  3. We collaborated with our legal team and external compliance consultants to ensure that our policies were compliant.
  4. We regularly reviewed our policies against regulatory requirements and made necessary adjustments to ensure compliance.
  5. We conducted periodic audits of our policies and practices to ensure that our policies were consistent with regulatory requirements.

As a result of our compliance framework, we were able to meet regulatory requirements and pass multiple compliance assessments by independent auditors without any issues or violations. Our API rate limiting and throttling policies were evaluated as being robust and effective, giving our customers confidence that their data was protected and secure.

9. What methods do you use to ensure that the API rate limiting and throttling policies are scalable and can handle future growth?

As a seasoned API developer, I understand the importance of scalability when it comes to API rate limiting and throttling policies. To ensure that these policies can handle future growth, I implement methods such as:

  1. Load testing: To test the maximum number of requests that can be handled by the API, I use load testing tools like JMeter, BlazeMeter, and Gatling. This helps me identify the bottlenecks and optimize the API performance accordingly.
  2. Cloud hosting: Cloud hosting platforms like AWS and Google Cloud Platform provide scalable infrastructure services such as load balancers and auto-scaling groups, which can help handle sudden spikes in traffic to the API. I have experience using these services and familiarizing myself with how they work.
  3. Horizontal scaling: By adding more instances of an API service, I can distribute the load and increase the API's capacity to handle more requests. This method ensures that the API can handle future growth by scaling horizontally.
  4. Centralized monitoring: Having a centralized monitoring solution enables me to easily monitor the API's performance in real-time, allowing me to identify any issues before they cause downtime. With the use of tools like Splunk, Kibana or Grafana, it is possible to monitor key performance indicators(KPIs) across all APIs.

With these methods, I have been able to handle massive traffic loads and ensure that the API rate limiting and throttling policies remain efficient even as the API continues to grow. Notably, in a project dealing with a video streaming API, I was able to handle about 50,000 requests per minute with an average latency of 120ms over a nine-month period with a team of 3 developers. With such results, I am convinced of my capability to ensure optimal performance and scalability of API rate limiting and throttling policies in both present and future systems.

10. What emerging trends and technologies in API rate limiting and throttling are you keeping an eye on?

As a tech enthusiast, I always keep an eye on emerging trends and technologies in API rate limiting and throttling. One of the most exciting technologies that have caught my attention recently is the use of AI and machine learning to optimize API throttling.

Companies like Google have already adopted AI algorithms to limit the number of requests from abusive sources in real-time. The system analyses patterns of incoming requests and reacts dynamically with limits and temporary blocks. The technique reduces the overall latency while still protecting the API from unnecessary load.

Another technology I'm keeping an eye on is the implementation of Serverless architecture for API throttling. With Serverless, you can specify auto-scaling rules for your functions, and the infrastructure will respond proportionally to the number of incoming requests. Using Serverless architecture for API throttling allows for increased efficiency and scalability regarding system resources, enabling the processing of more requests without crashing or permanent damage to the system.

  1. In which ways would you incorporate AI in API rate limiting?
  2. What advantages does Serverless architecture offer for API throttling, and how would you use it in production?
  3. How does AI-based throttling compares to traditional rate limiting systems in terms of efficiency and cost?
  4. What is your experience with setting up API throttling rules and policies?


Congratulations on finishing the "10 API rate limiting and throttling interview questions and answers in 2023" blog post! Now that you’re equipped with new knowledge, it’s time to take the next steps towards landing your dream job as a remote API engineer. Don't forget to write a compelling cover letter to capture the attention of potential employers. To build an impressive CV, take a look at our resume guide for API engineers. Finally, if you're ready to take the leap and search for remote API engineer jobs, our website job board is the perfect place to start. Good luck in your job search and future career endeavors!

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