Best Practices to Design RESTful APIs

As a developer, your goal is to create systems that are future proof and easy to maintain. This is easier said than done, especially if you’re designing REST APIs as there are no industry standards or a golden book of principles to follow. For many, simply developing to stay compliant with the REST architecture is enough. But, it isn’t. The common approach is to work within the six limits of a RESTful system, which are:

• Layered system
• Client-server architecture
• Statelessness
• Cacheability
• Uniform interface
• Code on demand

While this does offer functionality, it doesn’t promise any type of sustainability. This is important because poorly designed REST APIs pose a problem for clients using the APIs and professionals that maintain the APIs. In addition to that, it adds a great deal of frustration to the entire process and this cascades into another set of issues. For instance, developers working with a poorly defined API are likely to abandon the services altogether and set out on a mission to do it themselves. As a result, there is a high chance of duplicating functionality, which isn’t good for anyone.

To put things into perspective, it helps to remember that REST APIs are essentially the face of any given service. Naturally, the primary requirement is that they are easily recognised, and their semantic behaviours should be easy to understand. This can be a challenge for some developers due to the lack of standard developing rules. Thankfully, there are companies and experts that stick to a reliable set of conventions to ensure optimal development of REST APIs. To know more, take the look at these best practices to design RESTful APIs.

Use the right type of web framework

A good practice to keep in mind when developing REST APIs is to use the best tools for the job. When designing an API, regardless of what for, most developers will revert back to a framework they are comfortable with and this isn’t always the best decision. Think of it as using a flathead screwdriver when the situation calls for a Philips head variant. The latter is a better fit, probably requires less effort and reduces the chances of issues by a great degree.

In this case, Python developers would likely rely on Flask, where JS developers would go to Express, and these would be the tools to implement the requirements to handle HTTP requests. While this may work successfully, neither of these frameworks is designed for building these types of REST API servers. Despite their versatility as frameworks, you would have to invest a great deal of effort to stay REST compliant. Owing to the extra effort and skill involved, many developers are also likely to skip over the polishing and will leave consumers with a less-than optimal API.

Naturally, the solution here is to use the right frameworks, and these are usually ones that are designed to build REST APIs efficiently. In Python, Falcon is a smart option and can help these developers develop these APIs within minutes. For Django-proficient developers, Django REST is known to be incredibly powerful and intuitive. Lastly, for NodeJS developers, Restify is a reliable framework that several developers can stand behind.

Deal with errors by returning standardised error codes

When handling errors, the first rule should be to eliminate the possibility of any confusion among the API users. A good way to do this is to use standardised HTTP response codes accurately so that the API maintainers have enough context about the problem. Many developers fail in this regard and these errors go unchecked, resulting in a problem for the final API consumer.

To avoid this problem, here are the common error HTTP status codes:

• 400 Bad Request: This is when the client-side input fails validation.
• 401 Unauthorized: This should appear when the user isn’t authorized to access the data or isn’t authenticated.
• 403 Forbidden: This error code should appear when the user is authenticated but doesn’t have access.
• 404 Not Found: This should appear when the resource is missing or isn’t found.
• 500 Internal server error: This is a very generic error and shouldn’t appear explicitly.
• 502 Bad Gateway: This should appear when there is an invalid response from an upstream server.
• 503 Service Unavailable: This error should appear when there is a server-side problem.

These are the standardised codes to use, and it is the responsibility of the developer to ensure that these get thrown with sufficient context. This way, the maintainer has enough data to go on to troubleshoot effectively but attackers don’t have enough to find vulnerabilities and bring down the system. This part is important as simply throwing out an error without the necessary information is just as ineffective.

Understand the differences between error types

Security errors are quite common with APIs and many confuse the reason for an error. Experienced developers may sometimes struggle to determine whether an error is related to a mismatch with authentication or authorisation. In such scenarios, here are two pointers to keep in mind.

• If the user hasn’t provided credentials or if they are invalid, the 401 Unauthorised error code applies
• If the user has provided credentials and they are valid, then the 403 Forbidden error code applies.

Replace verbs with nouns in endpoint paths

It is an unspoken rule among several developers that you shouldn’t use verbs in the endpoint paths. The main reasoning for this is that the HTTP request method already contains a verb and inserting another doesn’t have any use. All it does it lengthen the endpoint path and also fails to convey any new information. Typically, the verb chosen should be in line with the HTTP request method. For example, GET, PUT, POST, and DELETE are common methods, for which:

• GET is used to retrieve resources
• PUT is used to update the data
• POST is used to submit new data
• Delete is used to remove data

Get used to versioning

Versioning your REST APIs is a healthy habit to inculcate, especially when you anticipate that something you’ve designed will require constant tweaks. Whether you need to change a specific action, data structure or introduce a backward compatible change, the best way is to have dedicated versions for these. An added benefit of versioning is that it allows you to improve a service while ensuring that your API’s users aren’t lost due to a change.

In some situations, API users are reluctant to alter their integrations to welcome a change on their end and without versions, they’d have no other option but to drop the API. Generally, there are 2 ways to go about versioning.

• Implement the version in the request header
• Implement the version in the endpoint URI.

From the two options, the second one may be a better choice as it facilitates discoverability and readability in a more effective manner.

These are some of the best practices to keep in mind when developing REST APIs, and you should definitely make them part of your arsenal to stay competitive. It is the adoption of small but meaningful changes like these that will help you take your skill to the next level.

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