Let’s Compare And Contrast Koa and Express

6 min readApr 10, 2021

In order to learn about KoaJs and ExpressJS first, we have to learn what NodeJS is because both Koa and Express are web frameworks that are running on NodeJS.

NodeJS

First of all, NodeJS is not a programming language or a framework. NodeJS is an open-source, cross-platform runtime environment that is created from JavaScript that runs on V8 engines. Since it is a runtime environment, most frameworks run on NodeJs in order to build back-end services like Apis, Web Apps, and Mobile Apps. Due to the use of event-driven and non-blocking I/O model Nodejs become more efficient and lightweight.

ExpressJs, KoaJs, NestJs, and SailsJs are some of the frameworks that run on NodeJS

KoaJS

KoaJs is an open-source backend web application framework that runs on a NodeJS environment. The same creators of ExpressJS are maintaining the KoaJS also. Due to its minimal and flexible features, we can have a set of features that are needed for web and mobile applications. When comparing to other frameworks that run on NodeJS, this is the most popular web framework. This framework aims for becoming smaller, more expensive and to have a strong foundation for web applications and APIs.

Koa uses asynchronous functions to allow you to eliminate callbacks and increase the efficiency of error handling and Koa does not bundle any middleware within its core. It provides an elegant suite of methods that make writing servers fast and enjoyable.

ExpressJS

ExpressJS is a free, open-source backend web application framework which is created by a developer called TJ Holowaychuk. This also runs on NodeJS and same as KoaJs this also has some features needed for web and mobile applications because of its minimal and flexible properties. This is described as a Sinatra-inspired server because it is relatively minimal with many features as plugins. This enables the user to multiple HTTP requests at a specific URL. This also used to create APIs and due to its myriad of HTTP methods and middleware at disposal creating API is become easier.

Express is a popular backend component for full-stack development like MERN and MEAN stacks. Together with front-end JavaScript frameworks like React and Angular with MongoDB database following NodeJS runtime ExpressJS became the backend framework for those stacks.

Now let’s compare and contrast KoaJS and Express JS

Installation

In order to install express and koa, we need to npm (node package manager)

Express

When the npm package installed, we can install express using commands

There are two ways to install express

Installing express permanently (After installing express will added to dependency list)

2. Installing express Temporary (After installing express will not be added to dependency list)

In order to call methods of express, we have to import the express module

Koa

Same as ExpressJS, KoaJS need to install Node.JS. Here Koa requires node v7.6.0 or higher version for ES2015 following with async function.

In order to call methods of koa, we have to import the koa module

Performance

When we compare Koa and Express performance-wise Koa is more ahead of Express. This is because in koa we can stop using callbacks, it deals with errors very quickly as well as koa is a very lightweight framework.

Below shows the performance request per second for the “Hello World” app

Source: https://nodesource.com/blog/Express-Koa-Hapi

But there are best practices that can be used for improving the performance of both frameworks

Koa

Use asynchronous APIs
Keep codes small and light
Use gzip compression

Express

Use gzip compression
Don’t use synchronous functions
Handle exception properly, using try-catch or promises

Popularity

When compared to Koa Express became more popular in the community (This is compared with Github starts and Downloads per week). This is because beginners are more comfortable using Express. This is due to the trend of building native applications.

Advantages

Let’s discuss the advantages of KoaJs and ExpressJs

Advantages of ExpressJS

Very stable Node.js web middleware
Flexible and scalable
Fast app development
Fully customizable
supported by extensive documentation
has excellent community backup
Enough resources to debug
Easy to integration
Don’t need multiple dependencies to cover the framework

Advantages Koa

Koa improves interoperability, robustness, and enjoyability of middleware
Koa is very lightweight with 500 lines of codes
Has a large number of helpful methods with small footnotes
Has a very good user experience
Better error handling through try/catch
Generated-based control flow
Cleaner, more readable async code

Disadvantages

Even though there are advantages we have to consider disadvantages of those also

Disadvantages of Express

There should be a clear environment to avoid problems when maintaining the codes
When the codebase increases refactoring becomes cumbersome
A lot of manual labor is required due to the creation of endpoints
It doesn’t have any built-in error handling like Koa and Hapi

Disadvantages of Koa

The open-source community around Koa is relatively small
Not compatible with Express-style middleware
Generators used for Koa not compatible with other middlewares of NodeJS frameworks

Final Thoughts

As we discussed earlier Koa and Express are backend frameworks which mostly used on mobile and web applications. When comparing those two frameworks both frameworks are best in each of their areas.

When you consider Koa,

Koa is cleaner than express and performance-wise more ahead than it. When considering the asynchronous performance, Koa has async/await support for asynchronous flow also. For a person who needs a simple reference for a framework as a footnote, Koa is the best choice to make

Sametime,

Express is lightweight and minimalist and Express is more popular than Koa since, for a person who needs a complete framework without having multiple dependencies, express is the best

Therefore even though we cannot say Express or the Koa is the best when comparing various features of them