An application programming interface (API) exposes the data of an application for use by other programs, called consumers. An API acts as an agreement between two systems to share data using a specific language and format.
Your choice of API architecture is tightly coupled with your application’s non-functional requirements, which describe how you want it to behave and provide its main functionality.
Designing an effective API includes considering which design patterns to use, which architectural components to have, and how requests and responses flow between your consumers and data sources. A well-designed API architecture is easy to use and maintain, scalable, handles data and interactions securely, and is amenable to extension as new technologies and practices become available.
Modern API strategies also focus on reducing monolithic design patterns, often by exposing application logic and resources through containerized microservices and serverless functions. This trend has encouraged APIs to be lightweight, modular, and resilient.
Components of API Architecture
Effective use of APIs requires careful planning from the beginning of an app’s development. It’s essential to define and adhere to architectural boundaries that separate the management of data handling, internal services, and interactions with other applications.
When designing your API architecture, it can be tempting to build out portions of your application and then build your API around how the software functions. However, the benefits of APIs come from modeling your API architecture around the consumer’s needs.
The following points should all be considered designing an effective API. For each component, we’ll review how to optimize an API’s architecture with that component in mind.
Scalability describes an API’s ability to handle large amounts of concurrent requests without slowing down or crashing. As your application sees more traffic, your API must be able to accommodate this growth. In addition to performing better, a scalable API is easy to upgrade in the future.
Using an Async API
You’ll likely use an event-driven, asynchronous (async) API in a massively scalable application. This ensures that no single request will slow down service for the rest of your high-volume traffic.
An event-driven API responds to individual events as they happen without necessarily executing them in the order in which they were received. It’s particularly suitable for streaming or IoT applications.
Using an RPC API
Additionally, you could use a remote procedure call (RPC) API internally. This lets your application’s back-end components remotely call procedures rather than requesting and sending data. It also lets you treat your internal infrastructure more like a single, pooled hardware resource rather than a set of separate components.
Using a Load Balancer
Other optimizations include infrastructural tuning. For example, a well-configured load balancer ensures that requests are sent to the instances that can best handle them.
You can also create a responsive system even over large geographical distances by caching responses, using a content delivery network (CDN), and configuring timeout durations to account for increased latency and network overhead.
Security is one of the most significant factors affecting your API architecture design choices. Because an API often exposes a large pool of your resources and infrastructure, attackers can leverage an improperly designed API to cause significant damage to your production or clients.
Establishing Security Measures
To safeguard against denial of service (DoS) and injection attacks, you’ll need to determine which messaging protocols and API types are most appropriate for the different portions of your architecture.
Your choice of technology needs to support the proper level of in-transit and at-rest data security and authentication, so it’s essential to integrate with a rapidly evolving set of identity and access management (IAM) tools and encryption standards.
Using an API Gateway
An API gateway is the most critical component for securing your API. In addition to acting as an API proxy, a gateway is an enforcer of security configurations and allows you to categorize your architecture and provide more fine-grained access to resources.
Additionally, an API gateway can provide detailed logging and analytics functions, as most or all of your application’s traffic should pass through this gateway.
To successfully monitor your system, remediate any errors, and improve your application, you must be able to collect data. This process begins with thorough and consistent logging practices.
Using Logging via an API Gateway
You can implement logging functionality through an API gateway. You should consistently record and store API calls and the network traffic they generate, tagging them with descriptive metadata. This makes it easier to integrate your data with your day-to-day analytics, incident responses, and any processes that require external auditing for regulatory compliance.
Using Analytics Tool
Once your data is logged and stored, you can process it with a variety of analytics tools. Running business analytics uncovers monetization opportunities, while developer analytics ensures that your teams can remove performance bottlenecks or potential security vulnerabilities and create a product that is easier to consume.
With these factors in mind, you can now decide on the best type of API architecture to use for each part of your system.
An API gateway can act as a front end for an API, providing a single entry point for external consumers. By insulating clients from back-end implementation details, an API gateway provides a uniform interface that lets clients use a familiar and simplified language regardless of the application’s back-end complexity.
You can also configure your API gateway to issue tokens and enforce rate limiting and throttling, which are considered indispensable in any modern service. This lets you implement a more modular authentication flow.
Architectures without an API gateway rely on providing the consumer access to each service or service mesh. It can quickly become challenging in complex architectures to maintain securely accessible, up-to-date resources.
API gateways let you create more complex architectures that are easier to secure, modularize, and extend with new integrations. This is particularly useful in microservice architectures or mobile applications, in which an API gateway ensures that consumers use an interface that’s well-matched to their needs.
However, API gateways aren't always appropriate for ultra-low-latency data streaming. The additional network hop can negatively impact the performance of real-time data streaming applications.
Still, doing away with an API gateway means you must implement its functionality through a service mesh — which creates more work for each node on the network — or through the protocol itself. This means that APIs consumed by IoT applications or those on edge networks demand extra attention to weigh the tradeoffs of each architecture decision.
Most web APIs use a REST (sometimes called RESTful) architecture. RESTful APIs are scalable, lightweight, easy to use, and almost universally supported.
This predictability benefits your API’s security and analytics, as there’s a large base of established best practices and tools for reliably managing RESTful interfacing.
For example, it’s standard practice to ensure that all GET requests to your API are idempotent. This means that each identical GET request to an endpoint should always return the same response, no matter how many times it is sent. This requirement is part of the standard criteria for API test suites.
In contrast to RESTful API architectures, APIs based on the simple object access protocol (SOAP) are unpredictable. They tend to be highly platform-specific and often present non-uniform interfaces that differ in each implementation.
These qualities have several implications for architectural API decisions. By default, clients must interface with a service that’s less discoverable than one using a RESTful API. This obscurity can contribute to a SOAP API’s perceived security, and a SOAP API can be designed with a focus on security. Still, the API is more complex to implement and less flexible in the long term.
This makes SOAP APIs better suited for an organization’s internal data management. For example, an enterprise may offer an outward-facing REST API, exposing its application to clients through an API gateway. Behind the gateway, traffic is routed through the enterprise’s internal network using a SOAP API. This allows the business to present a predictable, accessible, and lightweight interface for public use while retaining an internal API tailored to their business logic.
And, because the API gateway handles basic security, the enterprise has more flexibility to implement custom SOAP interfaces and zero-trust security on their internal network in other ways.
An event-driven architecture using an asynchronous approach lets you isolate processes using workers and complete requests without slowing down the application. A framework like Node.js, for example, is designed around splitting apart and handing off functionality to be independently executed by worker processes, which return to the primary process whenever they finish.
You can even build on the strengths of an asynchronous architecture by using a lightweight protocol like gRPC, which transmits data in a binary format and supports rich error codes. This lets you create a low-latency distributed back end with robust logging capabilities.
Build the best API for your business.
The benefits of thoughtfully designed API architectures are difficult to overstate: They enable a more agile business that can operate as a collection of smaller, product-oriented teams. This allows developers and IT operators to rapidly and reliably deliver and maintain robust software with less overhead and downtime.
An application designed around its API does more than meet the functional requirements of its users. It also presents an easy-to-manage back end for your developers and service teams. The result is an application providing its users agile, secure, predictable, and fine-grained access to the resources they need. Additionally, comprehensive logging and analytics also simplify auditing and remediation if an attacker overcomes your security measures — which are often best implemented in an API gateway.
When creating a new application, designing an API architecture should be one of your first considerations — well before you start writing the application code. Selecting the right API type and architectural components ensures you’ll be able to provide a service that scales with your success and provides enough analytics to get the most value from your investment.