6 Features of Good API Design
APIs are the building blocks of modern software. According to the 2022 State of the API Report, 51% of organizations spend more than half of their development effort on APIs.
From the creation of an API to the time it is retired, multiple developers come in contact with it and use it to access relevant data and functionalities. That means APIs have to be secure, reliable, scalable, and easy to update. Well designed APIs have a longer life cycle because they can be enhanced instead of being retired when user requirements change. When working on your next API, make sure they have these six features.
1. Consistency in Naming Conventions and Response Formats
Consistency results in efficiency and error prevention. Without consistency in naming conventions and response formats, it would be difficult for developers who didn't create the API to work with it. When the naming conventions, parameter orders, and response formats are consistent throughout the API, any developer can quickly grasp the patterns and structures.
Consistency becomes even more important when dealing with multiple APIs that support an app. For example, a social app may use a chat API, an authentication API, and a social feed API, among others, with each API serving one specific purpose. When all of these APIs follow the same naming conventions and data formats, the developers responsible for the app find it easier to work with them and have a positive experience.
2. Reliability Under Heavy Load
An API should remain available and perform as per user expectations even under heavy load. For that to happen, its infrastructure, effective use of load balancers and caching, and rate limiting all come into play.
Infrastructure — like servers, network components, and databases — is the most important factor that affects the reliability of an API. If you have a scalable infrastructure in place, your APIs will be available 24/7 and perform as expected, even under heavy loads.
To create an infrastructure that can handle heavy traffic:
- Use load balancers to distribute incoming requests across multiple servers.
- Add more servers to your infrastructure (horizontal scaling).
- Add more resources such as processors and storage devices to your servers (vertical scaling).
- Use cloud-based hosting services to scale up as needed.
- Choose scalable data storage solutions such as Cassandra or MongoDB and use sharding to handle increased data volumes.
- Use Content Delivery Networks (CDNs) to cache and serve static content, reducing the load on the API servers.
- Optimize API endpoints and payload sizes to minimize network latency.
It is also a good idea to cache frequently accessed data. This will reduce the load on the backend systems. In addition, rate limiting helps manage API load and ensures its availability. By setting appropriate limits on the number of requests per second or minute, developers can help the API maintain a consistent response time.
3. Security Against Common API Vulnerabilities
Security has to be one of the top priorities when designing an API. APIs are prime targets for attackers that want to breach an organization's network or gain access to its data.
There is no silver bullet when it comes to protecting APIs from multiple types of attacks. Each type of attack warrants a different security measure.
- SQL Injection: In this type of attack, attackers inject malicious SQL code into user inputs and gain access to data. To mitigate SQL injection vulnerabilities, avoid using dynamic SQL queries and use parameterized queries or prepared statements.
- DDoS Attacks: In DDoS (Distributed Denial of Service) attacks, attackers send a massive volume of requests or traffic from multiple sources, making it difficult for the target to distinguish legitimate requests from malicious ones. Use rate limiting to protect your API from such attacks. If you identify some IP addresses making an unusually high number of requests, set a limit on the number of requests per second or minute for that IP address alone.
Some other best practices for API security include validating and sanitizing all user input, including request parameters, headers, and payloads. Use whitelisting or regular expressions to validate input and reject any suspicious or malicious data.
To protect your API from unauthorized access, use token-based authentication or OAuth 2.0 to authenticate users. Also, role-based access controls (RBAC) help you enforce granular access permissions and protect sensitive resources. Follow the principle of least privilege (PoLP) by granting API users the minimum required permissions. Regularly review and update access controls and permissions to prevent unauthorized access to sensitive APIs or resources.
Attackers continue to find new ways to exploit API vulnerabilities, so perform penetration testing and vulnerability scanning periodically to identify and address any potential threats.
4. Accessibility Through Secure Authentication and Authorization Mechanisms
You want your API to be available to everyone who is authorized to use it. For that to happen, use the following authentication mechanisms:
1. Token-Based Authentication is a method of verifying user identity by issuing a unique token that serves as a credential for accessing protected resources. Include JSON web tokens (or API tokens) in subsequent requests as proof of authentication.
2. OAuth 2.0 is an authorization framework that enables third-party applications to access user data from a service provider on behalf of the user, without sharing the user's credentials. Set up an authorization server to issue access tokens to the client and use a resource server that validates these tokens to grant or deny access.
3. OpenID Connect is an identity layer built on top of OAuth 2.0, providing a standardized way for users to authenticate and authorize their identities across different websites and applications. Build OpenID Connect on top of OAuth 2.0 and issue identity tokens to each user so they can benefit from single sign-on (SSO).
4. API Keys are unique alphanumeric codes or tokens assigned to developers or applications, used to authenticate and control access to specific APIs or services. Generate a unique key for each client so they can send it along with their API requests for authentication.
5. Multi-Factor Authentication (MFA) is a security mechanism that requires users to verify their identity using multiple independent factors, such as passwords, biometrics, or hardware tokens, to gain access to a system or application. Add another factor of authentication, like a temporary code sent to the user's registered mobile device or email address.
Not all of these mechanisms will apply in all situations. For instance, you will rely on API keys in most cases and won't have to use MFA unless you have a public-facing API. Regulatory compliance will also come into play when dealing with products and APIs in the healthcare and finance sectors, and you will have to be extra careful not to expose sensitive data to unauthorized users.
5. Flexibility Throughout the API's Lifecycle
Good API design accounts for the need for the API to evolve with time. There are many reasons for an API to be maintainable and easy to update—the application may need to be updated, user requirements may change, or better technology may come along—any of those reasons may prompt you to make changes to the API.
To make your API easy to update, make sure you have detailed API documentation and follow versioning standards and best practices.
Documentation is the first thing any developer wants to look at when working with an API. Use tools like Swagger or OpenAPI to generate interactive documentation, and document every minute detail related to your API. Your API documentation should contain the purpose, functionality, and usage of each endpoint, the required parameters for each endpoint, response formats, code snippets, and examples.
Besides documentation, versioning is another important aspect of maintaining an API. Every time you make changes to an API, you are making a new version of that API. So, follow the standard procedure of using version numbers in the API endpoints or headers to distinguish between different API versions. Also, provide regular updates to your team and all stakeholders about version updates so everyone knows what's different in a new version. This way, any developer working with a specific version of the API will know exactly how to use it.
In addition, use peer reviews to identify potential issues in the codebase of your API.
6. Extensibility, So Changes Don't Break Your API
Extensibility in API design means developers can enhance the API with new features, capabilities, and resources without breaking existing functionality. You should design the API in a way that other developers can add new endpoints, parameters, or response fields and modify or depreciate existing ones without affecting the experience of the users of that API.
Extensibility can be achieved by separating each function of the API into an independent module, allowing for separate development, maintenance, and extension of each component.
On top of that, extensible APIs have hooks or extension points that allow clients to customize or extend the API's behavior without modifying the core functionality. These hooks are self-contained functions. For example, Salesforce uses before, after, and modify response that developers can use to add custom logic or override default behavior as needed.