What is the API lifecycle?

APIs are sets of rules or protocols that enable software applications to communicate with each other to exchange data, features and functionality. There is both an API producer lifecycle—focused on the creation and distribution of APIs— and an API consumer lifecycle, centered on API use from the consumer’s point of view. This article focuses on the API producer lifecycle.

There isn’t one universal API producer lifecycle. You might see different variations from different sources, but the lifecycle generally includes the following stages: plan, design, develop, test, deploy, monitor and retire.

API management platforms are often used to help organize efforts across an API lifecycle, and to centralize API strategy, governance, documentation and directories across an IT environment. Many platforms include advanced analytics capabilities and tools for API discovery and monetization that help organizations get the most out of their APIs.

A consideration and understanding of the entire API lifecycle helps development teams allocate resources more efficiently, create realistic timelines for delivery, keep all stakeholders informed throughout the process and ensure that APIs meet business requirements. Essentially, a well thought-out and executed lifecycle helps deliver high-performing, secure APIs and a stronger user experience.

End-to-end API lifecycle management comprises several key stages, beginning with preliminary planning and ending, often, but not always, with retirement or replacement. As an example, let’s consider a software company that decides to build an API to sync its customer data with business tools such as support ticketing, accounting systems, project management platforms and more.

Building an API begins with answering some fundamental questions: Why is this API needed, who is it for, how will it be used and how will success be measured? 

Specificity about the goal of the API project can help clarify what features and functionality the API design needs to have. In the software development example, the goal of the API is to ensure that customer data can move seamlessly between applications and platforms that the company uses or plans to use. 

In this planning phase, organizations:

• Review the potential business benefits of the API
• Describe how this API will address business needs
• Ensure that there are no existing APIs or other available products in native integration marketplaces that could do what’s required (essentially, confirming that building this API is necessary)
• Clearly delineate which applications and platforms will rely on the API and how the API will integrate with existing workflows.

Next, the team should discuss potential users and use cases. Is this purely for internal use? Which teams will be using this API, and for what? Are there security concerns that should be addressed in the design and development phases? And crucially, who will be responsible for each phase of the API’s production?

Setting a timeline for completion of the project helps ensure that the project stays within budget. Importantly, timelines must be realistic and flexible. 

Teams will answer questions like: Are there any specific dates, such as a new feature launch date, which must be met? Are there security or legal compliance teams or other stakeholders who need to sign off before this API can be deployed? 

Where will documentation and other information about the API be stored and made available to developers and users alike? Where will code changes be tracked and stored?

Answering these types of questions at the outset helps set a clear plan for the rest of the lifecycle.

While the planning stage describes the desired outcome, the design stage defines how the team plans to get there. Throughout the design process, the API design team decides how the API should be built in order to satisfy the requirements detailed in the planning phase. 

The team must make design decisions concerning the protocol and architectural style the API will use. This decision might be based on the existing API architecture at the organization, or on the intended use cases for this new API.

For example, common API frameworks and architectures include REST, GraphQL and gRPC; each has its own strengths and weaknesses. 

• REST: Simple, intuitive and ubiquitous, but not ideal for complex queries and does not offer strong typing.
  
  
• GraphQL: Efficient, with strong typing and built-in documentation. But GraphQL can also be complex and require more setup and specific expertise than REST.
  
  
• gRPC: Fast, with strong typing, automatic code generation and bidirectional streaming. gRPC is often used for microservices communication. But as a newer framework, there can be a learning curve, and its documentation format is binary rather than human-readable. 

In designing the API, the team will also decide what type of authentication is appropriate (such as OAuth 2.0) and if the API should sit behind an API gateway.

A specification document describes the structure, behavior and functionality of an API in a standardized way. It provides a single source of truth with information on how the API is built, what it can do, and how to interact with it. 

The most popular standardized specification is the OpenAPI specification, which allows developers to define paths, methods, parameters, authentication methods and more. OpenAPI is specifically used for REST APIs and supports a set of open-source tools called Swagger, which offers code generation, editing and automatic documentation creation.

For GraphQL, the equivalent specification is the GraphQL schema, a strongly typed contract written in schema definition language, or SDL, a human-readable format. The GraphQL ecosystem offers a few different tools that leverage this schema in ways that offer similar functionality to OpenAPI; for example, GraphiQL is an in-browser integrated development ecosystem (IDE) for developers to use as a sandbox. 

For gRPC, Protocol Buffers, or protobuf, is a serialization format and interface definition language (IDL) which serves as the most commonly used file format for specifications. Protobuf does not offer interactive testing, though there are web UIs that allow for this. 

In this stage, developers begin coding, following the API design plan outlined in the previous step. A version control system is used to track versions and code changes throughout the development process.

The industry standard for version control systems is Git, a piece of open-source software that tracks changes in code stored locally on a developer’s device. Developers use Git to create, manage and track changes to their code, but then need a place for it to be accessible to themselves and others. 

GitHub is the most popular Git hosting service, offering both free and paid tiers, enabling the storage, retrieval and collaboration of Git code repositories. There are alternatives for hosting Git repositories, including GitLab, AWS CodeCommit and Microsoft Azure Repos.

API testing is conducted both during and after the API development phase; continuous testing aids development by revealing vulnerabilities and needs, and enabling regular updates. 

Unit testing involves isolating small parts of the code and testing them individually. In our software company API example, let’s say the team needs to test the response for a request to retrieve a user’s information. The GET command is intended to retrieve a user’s name and email address from that user’s ID number in a customer database. Unit testing would involve ensuring that this GET request retrieves the intended information and that a request for a nonexistent user ID returns an appropriate error message.

Integration tests are generally run after unit tests and are used to detect issues that unit tests miss. Integration testing helps ensure that multiple components or services can communicate as intended through the API. 

Going back to our example, let’s say that one feature of the API is that a webhook, or notification, is sent from one system to another in the case of a certain event, such as the addition of a new customer. To make sure this works, an integration test is set up with a fake server that receives a notification, and takes the expected action, when a new customer’s information is added to the CRM. This process is repeated for all integrations.

API contract testing ensures that an API does what users expect it to do. The contract is typically constructed as an OpenAPI specification file, which is a standard, machine-readable document that lays out the elements of an API’s functionality and capabilities. An API specification file is typically written in JSON or YAML and includes elements such as API endpoints, authentication methods, the specific formats of acceptable requests and responses, metadata and input parameters.

Assessing API performance commonly involves evaluating its speed and efficiency. In this stage, testers look to measure query response time, error rates, resource use (such as CPU and memory use), latency and throughput. Understanding the performance of an API in this stage can help reveal bottlenecks or redundancies that can slow down the user experience.

APIs are often used to transmit sensitive data, making security testing a vital component. API security testing essentially attempts to break the API in various ways to ensure safety and stability. Those attempts might include input validation testing to ensure data is only accepted when entered in pre-approved formats. 

Input validation testing looks for various types of attacks. Common types of attacks include SQL injection, in which bad actors insert malicious code into an application. SQL is a language used to communicate with databases, and certain universal SQL commands can trigger unauthorized responses, such as a list of all users. 

Other security testing methods include authentication testing, which ensures that identification security measures such as biometrics perform properly, and authorization testing, which ensures that users can only access the features they’re approved to access. 

Security testing is conducted both during and after the development phase, and new artificial intelligence (AI) features and automation are improving the strength and accuracy of these tests. AI security testing tools can automatically generate tests, scan code for bugs, analyze performance data to help predict issues and flag anomalous behavior, and much more.

In industries such as healthcare and financial services, regulations, laws and guidelines exist to protect the safety, security and privacy of users. Examples include HIPAA (American health information), GDPR (EU personal information) and CCPA (California personal information). 

Compliance testing is testing that ensures the API complies with any applicable laws and guidelines. For example, the GDPR grants the “right to be forgotten,” meaning that users can request the complete deletion of their data without undue delay. Compliance testing for a GDPR-compliant API would require ensuring that this rule is followed.

The deployment stage is the API’s launch. It’s been tested for functionality, security and compliance, and it’s ready to be used. In the deployment stage, the API moves from the test environment to the live production environment. There are several steps involved in deploying APIs.

Before deployment, the team should perform another review to ensure that supporting infrastructure, API documentation, user support, distribution and communication strategies, and monitoring protocols are all completed and ready to go. This checklist might include scaling servers, configuring alerts and notifications, creating an FAQ page, sending an announcement to customers (or a public announcement) and more.

CI/CD, which stands for continuous integration/continuous deployment, is a set of practices that automate and streamline software development, testing and delivery cycles. It is a fundamental practice within DevOps methodology. Like software applications, APIs are also commonly incorporated in CI/CD pipelines to streamline and automate the deployment, testing and updating of APIs. 

An API gateway is a software layer that provides a single entry point for clients to access a variety of backend services, or multiple instances of a backend service. API gateways can offer several advantages:

• Simplicity: Clients only need to keep track of a single service URL rather than many
  
  
• Load balancing: An organization can distribute traffic for a single service across multiple instances to spread out the load and avoid performance bottlenecks
  
  
• Security and governance: A gateway can be used to apply standardized security and governance protocols across many APIs. 
  
  
• Caching: A gateway can help with caching by storing frequently accessed data across multiple services. This helps accelerate responses and improve performance.

Organizations often issue beta releases to select users in order to test an API before fully releasing it to the public. This enables the organization to find and correct bugs, solicit feedback, measure performance and promote the API in a safer, more controlled environment.

Once the checklist and any beta launches are complete, it’s time to “flip the switch” and fully deplot the API. This process might include initiating distribution strategies to further inform internal or externals customers about the API and encourage its use. The distribution process might also include publishing user guides and other public outreach, updating a website or API directory, and adjusting settings to enable instant access rather than requiring private authentication.

One of the key benefits of understanding and planning for a full API lifecycle is ensuring that monitoring, observability and maintenance are a focus, right from the start. The job isn’t complete at launch; there’s still work to be done. API monitoring is an ongoing process, designed to see how an API performs in the real world, in real-time. 

Key metrics for monitoring include response time, or how long it takes the API to respond to requests; error rate, or the percentage of requests that fail; throughput and traffic, or the number of requests the API can handle; and infrastructure analysis, which measures the strain and health of servers.

The maintenance element comes in the response to the data gathered by the monitoring tools. Maintenance can come in the form of bug fixing, optimizing performance or even adding new features or capabilities.

In our CRM example, monitoring tools might detect that latency is high when customer data is sent from one platform to another; the maintenance phase can address this by reducing code redundancies, fine-tuning caching settings, or relocating servers to be nearer the customers they serve.

The end of an API’s lifecycle is just as important, dynamic and informative as any other stage.

Versioning is the extended process of maintaining an API’s efficacy through updates over its active lifespan. The key in versioning is to offer changes and improvements without breaking existing functionality for established users. 

For simple bug fixes and the like, updates are typically issued without applying a new API version, as these small changes are considered “non-breaking.” But for “breaking” changes, in which a new version is not backwards compatible with the version it aims to replace, it’s good practice to introduce the change as a new version.

Communication, both early and often, is key to versioning. A common practice is to support parallel versions: the older version remains active and functional alongside the new version, and developers communicate changes to urge users to migrate to the new version. Once all or enough users have migrated, the old version can be deactivated.

Retirement is the permanent removal and disabling of an API. Not all APIs are retired, but it’s common to eventually replace an API. There are several reasons why an API might be retired:

• A new version provides superior performance
• Compliance or security needs are no longer adequately addressed 
• Business or financial changes within the organization
• Incompatibility with newer software

After retirement, an API will be no longer functional. But there are a few stages that can help ease this transition.

Retirement of an API requires discussion. Is it necessary to retire the API, and why? What will be the alternative, if any? Who will need to be made aware of the impending retirement?

Typically, the organization will announce that an API is due for retirement. This announcement includes all necessary information for users of the API, such as why this change is happening, when it will happen and what actions the user needs to take, if any. 

Then the API is officially deprecated. The API at this point remains operational but will not receive new updates or features. The deprecation period is designed to give the user time and awareness to make any necessary adjustments.

The “sunset day” is when the public API is fully turned off, at which point requests will no longer be answered and clients attempting to reach the API will receive an error message. It’s good practice to update documentation to reflect this change, and to free up any server space or other infrastructure the API was using. 

A post-mortem on a retired API can be a useful exercise. Teams can discuss lessons learned over the complete API lifecycle and how they can be applied to future projects.