API Design First or Code First: Which Should You Choose for Your API?

API Design First or Code First

Now that the API industry is flourishing, developers, testers, and other stakeholders are putting a lot more thought into the particulars of their API design.In this regard, there are two main schools of thought. One camp of API developers advocates the “code first” approach, or coding the API immediately once given the go signal. Another camp swears by the “design first” approach, or designing the API first before any coding work even begins.

What are the deeper differences between the two? What advantages or disadvantages are there in choosing one over the other? And ultimately, which one of these is the right approach for your API product? Here’s a briefer on everything you need to know about “code first” and “design first” if you’re involved in the API’s planning and implementation.

The Difference Between Designing First and Coding First When Building APIs

First, let’s discuss what distinguishes these two approaches from each other.

Between the two, “code first” is considered the more traditional approach to API development. In this approach, the coding work for the API happens right after clients outline their business requirements. Oftentimes, it’s only after most of the coding work is done that a team will begin documenting the design of their API. Before standardization of practices was the norm in the API industry, “coding first” was the default plan of action. To this day, several developers will still choose to code first for reasons detailed further below.

In contrast, the “design first” approach is a fairly new philosophy to building APIs. But it has an increasing number of proponents and supportive technologies, like the Stoplight API design toolkit. The “design first” approach involves devising an API contract, or a shared understanding of how the API is supposed to function, before any coding starts. The API contract is both human-readable and machine-readable, and it acts as a guiding framework for any coding on the API’s services. At its core, “design first” is about putting a premium on the API’s design standard and using it as the key for consequent coding work.

“Design First” vs. “Code First”: The Pros and Cons

Both “design first” and “code first” are popular courses of action for developers. Neither of them is inherently superior to the other; it is more a question of which approach is best for your application.

The design-first and code-first approaches have their own sets of advantages and disadvantages attached to them. Here’s a quick comparison.

The Pros of “Design First”

  • Going for the “design first” approach will appeal to your team members who see the importance of planning. That’s because it’s necessary to draft the API contract before any coding ensues. Thanks to the API contract—which sets clear expectations for how the API will behave—everyone will be on the same page about subsequent coding work.
  • “Design first” is also a means of setting a standard and guaranteeing consistency in continuing API work. Thus, it’s the approach that’s ideal if your API team will develop multiple mission-critical services for an important client.
  • The API contract will act as a single source of truth, or point of reference that every developer on the project can refer to. Even after the initial API design is completed, the team can always go back to the contract for reference.
  • The “design first” approach often increases the chances of good developer experience, or (DX). Outside developers will see for themselves that there’s an underlying standard of quality running through the API work. This, in turn, will persuade them that their integration experience with the API will be a smooth, pleasant, and trouble-free one.

The Cons of “Design First”

  • Admittedly, this is often the more time-consuming approach among the two. Devising an API contract takes time, which may cause itchy feet among the more action-oriented members of the team.
  • “Design first” may also not be the most practical approach if the API team wants to prioritize speed, agility, and simplicity. The time and effort put into a “design first” approach may be excessive if the service being developed is a modest internal one.

The Pros of “Code First”

  • Between the two approaches, it’s “code first” that allows for faster coding work to be done.This can help an API company launch a product immediately for its own internal use. It is also the best approach for beating deadlines to take the API product to market.
  • This approach also works just fine for APIs that require fewer endpoints. In those cases, devising a brand-new API contract might even take more time than documenting and testing these endpoints.
  • In contrast to the “design first” approach, “code first” is a good framework for developing internal services that are meant to be simple. It is also fine for services that are meant to stand on their own, without any other companion services being in the pipeline.

The Cons of “Code First”

  • There’s a danger of inconsistent work being done if developers use only the “code first” approach for multiple services. The client may perceive each service to be of a different standard of quality, which could affect their trust in the API company.
  • There’s also the chance that, without a single source of truth and framework for action, you’ll spend time setting expectations and troubleshooting as you go.This can be tiring, time-consuming, and costly on your part.

Conclusion: Which Should You Choose?

Before settling on one approach, make sure to determine the business objectives for your API and what your priorities for its development are. Perhaps you need speed and simplicity, or perhaps you need consistency and the ability to meet mission-critical goals for large, omnichannel systems. Maybe your current ambition is to develop a simple, easy-to-use service for internal use. Or maybe it’s to create an entire network of services that all have the same invisible stamp of quality on them.

Regardless, be sure to choose wisely between “code first” and “design first”—and make your API’s success the first priority above all.

API Design First or Code First: Which Should You Choose for Your API?
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