Building and launching an Application Programming Interface (API) can seem like an intimidating task, especially if you’re new to the space and have limited experience working with APIs before. For the uninitiated, REST stands for Representational State Transfer and is an architectural style used to build APIs and services around data models. It is the most common type of API and one of the easiest to develop. However, REST API development still poses its own set of challenges for even the most seasoned developers.
- Why do companies develop custom APIs?
- Why is REST the most common type of API?
- REST API development best practices
Why do companies develop custom APIs?
Many companies develop their own APIs because they want to ensure complete control over how third parties access and interact with their data. Custom APIs give outside developers access to business logic so they can build their own apps without accessing a company’s proprietary code or frameworks.
If a company has a large proprietary codebase, exposing parts of it via an API can help drive adoption and promote consistency within a development team. If a company is looking to quickly expand its product line or service offerings, it may be able to do so faster by providing developers access to its data through an API rather than going through an internal approval process for each new feature.
Why is REST the most common type of API?
REST APIs have many advantages that make them the most common type of API: they’re simple to develop, easy to maintain, and flexible enough to suit nearly any web application. Additionally, REST offers one of the most straightforward ways to exchange data between different systems over the internet, particularly between web applications and servers. This is one of the primary reasons why REST has become the de facto standard for API development. Alternative APIs like SOAP and XML-RPC are still widely used in certain industries, but they are gradually being phased out by REST API.
Also read: What Are the Different Types of APIs?
REST API development best practices
To make sure your REST API development goes smoothly, there are several best practices you should keep in mind throughout the process:
- Document API changes
- Maintain consistent versioning
- Leverage formalized systems such as CRUD
- Use HTTP methods strategically
- Establish data structures and schemas early
- Understand your update options
- Choose compatible libraries and tools
- Anticipate error handling
- Enable content negotiation
- Plan for future growth
Document API changes
It’s important to keep track of any changes you make to your API using an API ChangeLog. Make sure everyone on your team understands exactly how each part of your API works and clearly documents every single piece. This is especially important when adding new features to your API; otherwise, bugs might creep into production without anyone knowing. Accurate logs will ensure consumers using your API don’t have to modify their code every time you update it.
Maintain consistent versioning
All new APIs should be versioned. Not only does versioning allow you to make changes as needed, but it also ensures that your API users can always find out exactly which version of your API they’re using and how they will be affected by any upcoming changes.
As such, all new APIs need an HTTP header (or possibly a query parameter) that provides version information at run time and defines version rules in its documentation. While there’s no one-size-fits-all way to version an API, it’s a good idea to follow a general convention like v1 or v2.0.x (where x is any valid integer) in order to let users know that it could change in future versions.
Leverage formalized systems such as CRUD
CRUD-based systems are commonly used for REST API development. CRUD stands for Create, Read, Update and Delete, and it refers to a method of managing data that uses Hypertext Transfer Protocol (HTTP) methods such as POST, GET, PUT and DELETE to define actions on database objects. The term often makes developers think of create new (i.e., POST), read from existing (GET), update existing (PUT) and delete from existing (DELETE). This approach allows developers using your API to interact with data in a similar way as they do with their own internal systems.
Use HTTP methods strategically
On a similar note, you’ll need to form a strategy at some point about the types of HTTP methods your API will use. POST should be used for creating resources and updating information about existing resources. GET should be used for fetching resources (it can also be used for fetching details about specific fields). PUT should be used only when performing partial updates. DELETE should be reserved for removing resources. You may want to consider using OPTIONS if your API will support operations other than those listed above.
Establish data structures and schemas early
When building a REST API, it’s important to make decisions regarding data structures/schemas early on, as these decisions can have significant implications on long-term functionality and performance. Here are some questions to consider before writing code:
- Can I use an existing data structure (e.g., lists, hashes), or should I create my own?
- Will each call return all of its results at once (returning all records for a query), or will there be pagination?
- How should I design these results when they return from an API call?
- How much data do I need returned from any given query?
- How should the code be formatted (JSON vs XML)?
- Does every client need access to every resource, or should certain actions take place behind the scenes?
A clear understanding of your business logic is critical in answering these questions.
Understand your update options
Deciding whether to provide only delta (or partial) updates can be confusing if you’re building a REST API that supports two-way updates. Your API may be consumed by the application software that stores its data in a database, in which case you may want to consider providing delta updates so you don’t end up consuming massive amounts of bandwidth and server resources. As with most things related to REST API development, understanding why these various options exist and when it’s appropriate to use them is key.
Choose compatible libraries and tools
The most common tools and libraries you will see when working with REST APIs are OAuth and OpenID. OpenID is used for authentication while OAuth is used for authorization—both have similar use cases. When looking at a package or library to work with your application, it’s important to make sure that it integrates well with what already exists in your stack.
Anticipate error handling
What happens when a user makes an invalid request or issues requests using incorrect data types? This is often one of the most overlooked parts of API development, but shouldn’t be left up to chance. Develop your API so it responds correctly to unexpected input.
Enable content negotiation
Whenever possible, allow your API to negotiate data formats. Doing so allows API users to specify in their request headers what kind of response format is desired (i.e., Content-Type: application/json) and ensures your API responds accordingly or redirects them elsewhere (i.e., 400 Bad Request) if it can’t handle that specific content type. It also prevents you from having to write several versions of every endpoint (e.g., /users/edit_user and /users/update_user) if you want to support multiple data formats.
Plan for future growth
Last but not least, keep in mind that API development never stops. Even if everything seems fine now, you might run into problems down the road as traffic increases. Therefore, make sure your API has room to grow by avoiding monolithic architectures and instead focusing on reusability, modularity, and abstraction whenever possible.
REST APIs can enhance applications
REST API development isn’t as easy as writing a web app or an HTML document. You must follow specific rules and best practices to ensure that your API is secure, reliable, and scalable. If you take things one step at a time, however, you’ll end up with an application that provides tremendous value to your users.
Read next: How Do APIs Work?