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Top 6 API performance metrics to monitor


When working on applications and systems, we usually rely on APIs to enable integrations between services that make up our system.

The purpose of this article is to provide understanding of some important API metrics that are used to measure an API's performance. For each of those metrics, I will also touch on some factors affecting them and ways to improve them, which will in-turn enhance your API’s performance.

Overview of the key API metrics

To cover the API performance metrics metrics in a comprehensive manner, I divided this article into two parts. In this first part, I will talk about three key metrics, which are Response Time, Throughput, and Latency.

1. Response Time

Response time is basically the time it takes for an API to respond to a request from a client application. Response time gives us a measure of our application's responsiveness, which in-turn has an impact on user's experience.

Factors Affecting Response Time

  • Network Latency is simply the delay in network connection between client applications and your API. Congestion and increased physical distance between servers in a network are examples of situations that impact network latency.
  • If you make use of external or third-party services, then the overall response times of your API will also be dependent on the response times of those services
  • The response times of your API can also be affected by slow or poorly written database queries

Monitoring Your API's Response Time

Monitoring and analyzing response time can help identify bottlenecks, optimize API performance, and ensure service level agreements (SLAs) are met.

There are lots of tools out there that can be used to monitor your API's response time. Here are some popular ones:

  • Apache JMeter
  • Pingdom
  • Datadog
  • New Relic

Improving Your API's Response Time

There are several approaches you can take to improve the response time of your API:

  • Making use of a Load Balancer
  • Optimizing your code to ensure to reduce unnecessary computations, database queries, or network requests
  • Implementing caching mechanisms
  • making use of content delivery networks (CDNs)

2. Throughput

Throughput is simply the number of requests an API can handle within a given time period. It is an important metric for measuring an API's performance, and is usually measured in requests per second (RPS)

An API with higher throughput simply means the system can handle a larger volume of requests, which ensures optimal performance even during peak API usage periods.

Monitoring Throughput

Monitoring throughput in the context of API performance involves analyzing and optimizing various factors such as

  • Server capacity
  • Network bandwidth,
  • Request processing time.

Improving Your API's Throughput

By employing techniques such as horizontal scaling, load balancing, and asynchronous processing, you can ensure a higher throughput which will significantly improve your API's performance.

3. Latency

Latency is another key performance metric for analyzing the performance of an API. It's a measure of the time taken for a client to send a request and get back a response from an API server.

Factors affecting API Latency

Some known factors that affect latency includes:

  • API Response with large data sets
  • Network Congestion
  • Inefficient or poorly written code.

How To Minimize Latency

It is very important to reduce latency, as higher latency can lead to sluggish user experiences, increased waiting times, and reduced overall performance. Some ways to reduce latency includes

  • Employing caching mechanisms
  • Applying data compression techniques
  • Returning data in chunks
  • Optimizing network protocols

4. Request Rate

Request Rate is an API performance metric that measures the rate or frequency at which requests are being made to an API within a specific time frame.

It provides insights into the load or demand placed on the API and helps gauge its capacity to handle incoming requests.

By monitoring request rate, API providers can identify usage patterns, peak periods, and potential scalability challenges which will help to anticipate traffic spikes, and plan resource allocation accordingly.

Monitoring API Request Rate

Request rate is typically measured over specific time intervals, such as:

  • Requests per second (RPS),
  • Requests per minute (RPM),
  • or Requests per hour (RPH).

The different measurement intervals determines the granularity of the metric and allows you to analyze the request patterns over different time periods.

There are several tools available to measure and analyze request rates for your API. Here are some popular options:

  • AWS CloudWatch
  • Google Cloud Monitoring
  • Grafana
  • Datadog
  • Prometheus

Optimizing For Higher Request Rates

To be able to handle increasing request rates during peak periods or as a result of high usage of some particular business features, you can consider implementing the following techniques:

Horizontal scalingUsing horizontal scaling techniques, such as distributing the load across multiple servers or instances. By adding more servers or utilizing cloud-based solutions that provides on-demand scaling of resources, you can handle a higher volume of requests by leveraging the collective resources of multiple machines
Asynchronous processingBy Identifying time-consuming or resource-intensive operations that can be performed asynchronously, you can free up resources to handle more incoming requests. This prevents blocking and allows your API to handle a higher request rate, if such operations are offloaded to background tasks or queues
CachingCaching can significantly improve response times and reduce the load on your API, especially for static or infrequently changing data. Utilize caching techniques like in-memory caches or CDNs can help your API to efficiently handle higher request rates

5. CPU Utilization

CPU utilization is another important metric that measures the percentage of CPU resources used during the processing of an API request. It provides insights into the efficiency of resource allocation and can be a key indicator of API performance.

Factors that can impact CPU usage during API processing include inefficient code implementation, highly computational operations, and the presence of resource-intensive tasks or algorithms.

Monitoring CPU Utilization

To effectively monitor CPU utilization, developers can employ various tools to gain insights into CPU usage. Some examples are New Relic, Datadog, or Prometheus.

Ways To Improve CPU Utilization

Below are some ways to reduce CPU usage within your API:

Efficient Algorithm DesignAnalyze your API code for computational bottlenecks and optimize them by using efficient algorithms and data structures. This will help to reduce CPU usage for operations that would have been more CPU intensive
Throttling & Rate LimitingImplement throttling mechanisms or Rate limiters to control request rates and maximum number of API calls that can be made within a specific time. This will in-turn prevent overload on the CPU.
Load BalancingBy making use of a load balancer, you can distribute incoming requests across multiple servers, effectively distributing the CPU load.

6. Memory Utilization

Memory utilization refers to the amount of system memory (RAM) used by the API during its operation. Efficient memory management is crucial for optimal performance. Excessive memory usage can lead to increased response times, resource contention, and even system instability.

Ways To Improve Memory Utilization

Here are some key points to consider to improve memory usage within your API:

CachingEmploying the use of in-memory caching mechanisms to store frequently accessed data or computations. This reduces the need for repeated processing and improves response times by serving precomputed results from memory.
Data PaginationWhen dealing with large datasets, consider implementing pagination rather than loading the entire dataset into memory, fetch and process data in smaller chunks or stream it to the client as it becomes available. This approach reduces memory pressure and enables efficient processing of large datasets.
Memory profiling toolsUtilize memory profiling tools to identify memory bottlenecks and areas of high memory consumption within your API. These tools can help you pinpoint specific code segments or data structures that contribute to excessive memory usage.


In this article, we discussed the importance of measuring API performance and some key metrics that tells us how well our API is performing.

Improving API performance as well as building SDKs for an API are some of the many problems that most API developers face. Here are liblab, we offer a seamless approach to building robust SDKs from scratch by carefully examining your API specifications.

By leveraging services like liblab, API providers can generate SDKs for their APIs, further enhancing their developer experience and accelerating the integration process with their APIs.