Performance & UX
·6 min read

API Response Times: A Quick Guide to Improving Performance

Application Programming Interfaces (APIs) are an integral part of the web and one of the core backbones for the different functionalities we see today. APIs are the technologies that allow us to connect with third-party services and tools, and it would be challenging to build innovative products without them.

Developers strive to build websites and applications that are feature-rich and perform optimally. API response time is one of the factors that can lead to significantly poorer website performance and influence user experience.

In this article, we will learn about API response time, the importance of measuring and optimizing response times, how latency affects overall site performance, and explore different ways of troubleshooting and improving API performance.

What are API Response time and latency?

API response time is the duration it takes an API to process a request and return a response to the client. It is one of the most common performance metrics used to evaluate the efficiency of an API.

Another metric for measuring an API's performance is latency. It is the time data spends traveling between the client and server. Response time is measured in seconds; latency is measured in milliseconds.

Users expect quick and seamless digital experiences more than ever before, and failure to meet these expectations can lead to a poor user experience, ultimately affecting our website's reputation and decreasing conversion rates.

A quick API response time and latency ensure that data is exchanged promptly between the server and client, resulting in a smooth and responsive user experience.

Factors that affect API response time

Here are some factors that can impact the response time of an API.

Server processing time

Server processing time is the time the server takes to process the API request, execute the required operations, and return the response. This is influenced by server hardware, database efficiency, and the complexity of the API's logic. Optimizing server processing time can be done by upgrading server hardware, caching frequently-used data, and simplifying API logic.

Network latency

Network latency affects API response time, depending on the geographical distance between the user and the server, network congestion, and the internet connection quality. Factors like distance can influence latency. We can minimize network latency by using Content Delivery Networks (CDNs) or hosting your API on multiple servers across different geographical locations.

Payload size

The size of the data transmitted between the client and server, also known as the payload, can significantly impact API response time. Large payloads take longer to transmit and process, leading to increased response times. To reduce payload size, consider using data compression techniques, removing unnecessary data from responses, and using efficient data formats like JSON.

Third-party dependencies

APIs often rely on third-party services or data sources to provide information or perform specific functions. The response time of these external dependencies can directly impact the overall API response time, particularly if they are slow or experiencing issues.

How to improve API performance

We can utilize several methods to improve the performance of APIs and boost their response times. Let's explore them in detail.

Use caching to speed up responses

Caching is a technique that stores the results of API calls to quickly retrieve them when the same request is made again. This eliminates the need for your server to process and send the same data multiple times, reducing processing time and bandwidth usage. Implementing Caching reduces the need for expensive and time-consuming database queries, which leads to substantial improvements in API response times.

Compress responses to reduce transfer time

Compressing API responses reduces the amount of data that needs to be received by the client. Doing this means that the response time of the API request is significantly reduced, as the payloads can be transferred efficiently. This, in turn, helps improve the API's overall performance, as the response times are faster and more reliable.

Optimize database queries

Slow database queries can have a significant impact on API response times. We can address this issue by ensuring our database is properly indexed, implementing pagination for large datasets, limiting the number of returned results, and minimizing the use of complex joins. Additionally, monitoring the performance of our database and identifying slow queries can help us pinpoint issues and implement appropriate optimizations.

Code optimization

Reviewing and optimizing our API code can lead to more efficient processing and faster response times. We can improve API performance by looking for areas full of inefficient code and refactoring them or switching to more performant algorithms.

Use asynchronous processing for long-running requests

Using asynchronous processing for long-running requests helps improve API response times by allowing the API to process multiple requests in parallel. This allows the API to process multiple requests simultaneously instead of waiting for one request to complete before beginning the next. This reduces the time required to respond to each request, resulting in faster response times for the API.

Implement load balancing to distribute requests

Load balancing helps improve API response times by evenly distributing the workload across multiple computers or servers. This helps reduce bottlenecks and latency and ensures the system can handle more requests without overloading one server. By doing this, the system can respond more quickly and efficiently to requests, resulting in faster response times.

Additionally, load balancing can help reduce downtime, as it ensures that if one server fails, the other servers can take up the slack and keep the system running smoothly.

Use a content delivery network (CDN)

A CDN is a network of servers distributed across various geographical locations, designed to serve content to users from the server closest to them. Using a CDN for our API significantly reduces the latency caused by geographical distance between the client and server, resulting in faster API response times.

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How does API response time affect SEO?

There are several ways in which API response time can affect SEO.

A slow API response time can lead to a poor user experience, which can, in turn, lead to a higher bounce rate. Google considers bounce rate when ranking websites, so a slow API response time can indirectly affect our website's SEO performance. For over a decade, Google has stated that it does not use bounce rates as a ranking factor. However, there is still contention over this, as some SEOs believe it does. Whether bounce rates are a factor or not, it is a metric we want to monitor and pay attention to.

Poor API response times can make it difficult for search engine crawlers like Googlebot to crawl our website. Googlebot uses APIs to crawl websites, so a slow API response time can make it harder for the bot to index our pages. This can lead to lower rankings in search engines.

A slow API response time can lead to slow website loading times, affecting Core Web Vital (CWV) metrics like Largest Contentful Paint (LCP), which measures the time it takes for the largest element on a page to become visible. The performance of an API can negatively impact SEO rankings if it contributes to a slow page speed or LCP.

Best practices for monitoring and troubleshooting API performance

Establish key performance indicators (KPIs)

Before diving into measurements, it's crucial to establish the KPIs that matter most to our application. Doing so will help us prioritize which aspects of performance to focus on, such as average response time, peak response time, or request throughput.

Utilize monitoring tools and techniques

We can use performance monitoring tools like New Relic, Postman, and Uptime Robot, which come with free tiers, and AppDynamics, Dynatrace, and Pingdom, with free trials, to monitor API performance. Leveraging these tools allows us to identify any potential bottlenecks or issues. They also provide insights on metrics like response times, error rates, and latency.

Analyze API logs

Server logs can provide valuable insights into API response times. Analyzing server logs helps us identify patterns and trends in API performance, such as slow response times during peak hours or specific endpoints that consistently underperform. We can use log analysis tools like ELK Stack (Elasticsearch, Logstash, and Kibana) or Graylog to help you visualize and analyze API log data more efficiently.

Monitor performance at different stages of development

Monitoring API performance is a continuous process, not a one-time activity. We should make it a point to measure response times throughout the development lifecycle, from the initial stages to post-deployment. This way, we can identify and address performance issues before they impact end-users, ensuring a smooth and efficient experience.


API response time is crucial in determining websites' and applications' performance and user experience. With users expecting quick and seamless digital experiences, optimizing APIs and measuring their performance continually is essential.

Factors like server processing time, network latency, payload size, and third-party dependencies can impact API response time. We can significantly improve API performance and achieve faster response times by addressing these factors and implementing performance optimization techniques.

Article written by

Nefe Emadamerho-Atori

Nefe is an experienced front-end developer and technical writer who enjoys learning new things and sharing his knowledge with others.

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Nefe Emadamerho-Atori

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