API Checklist

Request/Response APIs

REST API

1. Representational State Transfer (REST) is an architectural style for networked applications.
2. RESTful APIs use HTTP methods to perform CRUD operations (Create, Read, Update, and Delete) on resources.
3. Resources are identified by unique URLs, which are used to request or manipulate data.
4. REST APIs support multiple data formats, such as JSON, XML, and HTML.
5. Stateless by design, meaning each request must contain all necessary information for the server to process it.
6. Built on top of standard web protocols, making it easy to integrate with existing infrastructure.
7. Cacheable, which can help improve the performance and scalability of applications.

Use Cases

1. Web-based applications requiring CRUD operations on resources.
2. Mobile applications that require communication with a server.
3. Integrating with third-party services, such as social media platforms or payment gateways.
4. Implementing microservices architecture in complex applications.
5. IoT devices that communicate with a central server.
6. Public APIs for developers to consume and build upon.
7. Real-time applications where caching is important for performance.

Pros

1. Easy to understand, implement, and consume.
2. Utilizes standard HTTP methods and conventions.
3. Scalable due to its stateless and cacheable nature.
4. Multiple data format support (JSON, XML, HTML, etc.).
5. Wide adoption and numerous libraries and tools available.
6. Built on top of existing web protocols, which simplifies integration.
7. Self-descriptive, making it easier to maintain and troubleshoot.

Cons

1. Can be less flexible than other API types, such as GraphQL.
2. Over-fetching or under-fetching of data may occur, leading to inefficiencies.
3. Versioning can be challenging, as changes to resources might break existing clients.
4. Not as suited for real-time applications as WebSocket or other real-time APIs.
5. Can become verbose with complex nested resources.
6. May require multiple requests to retrieve or update related data.
7. Lacks native support for real-time updates or subscriptions.

Documentation

• OpenAPI Specification (formerly known as Swagger).
• Language-agnostic standard for describing and documenting RESTful APIs using JSON or YAML.
• Human-readable format that includes info about endpoints, request/response types, authentication, and other metadata.
• Swagger UI can generate interactive documentation from the OpenAPI Specification, enabling users to explore and test the API directly from their browsers.

GraphQL API

1. GraphQL is a query language for APIs developed by Facebook.
2. Allows clients to request only the data they need, reducing over-fetching or under-fetching.
3. Supports real-time updates using subscriptions.
4. Uses a type system to describe the data schema, enabling better validation and documentation.
5. Consolidates multiple API requests into a single request, simplifying client-server communication.
6. Provides an introspection system, allowing clients to discover the API schema at runtime.
7. Encourages a more flexible, client-driven development approach.

Use Cases

1. Applications with complex or nested data structures.
2. Mobile applications where data usage and performance are critical.
3. Real-time applications that require live updates and subscriptions.
4. APIs with evolving requirements, where clients need more flexibility.
5. Integrating with multiple microservices or third-party APIs.
6. Generating API documentation or client code automatically from the schema.
7. APIs that require fine-grained access control and permissions.

Pros

1. Highly flexible and customizable, allowing clients to request only the data they need.
2. Supports real-time updates and subscriptions.
3. Reduces the need for versioning, as clients can adapt to schema changes.
4. Simplifies client-server communication by consolidating multiple requests into one.
5. Provides a strong type system and introspection capabilities.
6. Encourages a client-driven development approach.
7. Can improve performance and reduce data usage in mobile applications.

Cons

1. Steeper learning curve compared to REST.
2. May be overkill for simple applications or APIs with limited data structures.
3. Requires a specialized library or tooling to implement and consume.
4. Potentially less efficient server-side, as queries can be complex and resource-intensive.
5. Caching can be more challenging compared to REST due to the dynamic nature of queries.
6. Security concerns may arise due to the flexible query system, necessitating proper validation and access control.

Documentation

• In the case of GraphQL APIs, self-documentation is a built-in feature, thanks to its introspection system.
• GraphQL APIs expose a schema that describes the types, queries, mutations, and subscriptions available, along with their input/output types and any applicable documentation.
• Clients can query the GraphQL server's introspection system to obtain this information, which can then be used to generate human-readable documentation.
• Tools like GraphiQL and GraphQL Playground provide a web-based interface for browsing, exploring, and testing GraphQL APIs based on the introspection data.

Remote Procedure Call (RPC) API

1. Remote Procedure Call (RPC) is a protocol that allows clients to call procedures on remote servers as if they were local.
2. Procedure-oriented, rather than resource-oriented like REST.
3. Supports various serialization formats, such as JSON, XML, or binary.
4. Can use different transport protocols, including HTTP, TCP, or named pipes.
5. Generally relies on specific function names and arguments to perform operations.
6. May use a service description language, such as gRPC's Protocol Buffers, to define and document the API.
7. Can be synchronous or asynchronous, depending on the implementation.

Use Cases

1. Client-server applications that require direct method calls on remote servers.
2. Service-oriented architecture (SOA) or microservices-based applications.
3. Internal APIs where procedure-based interaction is preferred.
4. High-performance applications that require efficient serialization and transport protocols.
5. Systems that need to support multiple transport protocols or serialization formats.
6. Applications that require fine-grained control over remote procedures.
7. Cross-platform or cross-language applications, as RPC can abstract away platform-specific details.

Pros

1. Procedure-based interaction closely mirrors local function calls, making it easier for developers to understand.
2. Flexible in terms of serialization formats and transport protocols.
3. Can support synchronous or asynchronous communication.
4. Efficient in terms of network communication, as it uses compact serialization formats.
5. Suitable for high-performance and low-latency applications.
6. Encapsulates platform-specific details, enabling cross-platform and cross-language integration.
7. Can use service description languages for better documentation and code generation.

Cons

1. Less standardized than REST, leading to more implementation variations.
2. May require additional tooling or libraries to implement and consume.
3. Less self-descriptive than REST or GraphQL, making it harder to discover and troubleshoot.
4. Tightly coupled to the underlying procedures, which can make it less flexible.
5. Potential for over-fetching or under-fetching of data, similar to REST.
6. Not as well-suited for web-based applications due to its procedure-oriented nature.
7. May require more manual configuration and management of endpoints and procedures.

Documentation

• If using gRPC (a popular RPC framework developed by Google), the preferred self-documentation method is through Protocol Buffers.
• Protocol Buffers (or "protobuf") is a language and platform-neutral serialization format used to define and document gRPC service interfaces, message types, and their associated fields.
• Developers can use the protobuf definition files to generate both client and server code in various programming languages.
• Tools like gRPC Gateway can generate API documentation based on the protobuf files, and tools like BloomRPC provide a GUI for interacting with gRPC APIs.

Event-Driven APIs

Webhooks

• Web hooks are a mechanism for sending real-time event notifications from one application to another over HTTP.
• A receiving application can register a URL to receive notifications when specific events occur in the sending application.
• Wide range of use cases, such as triggering a notification when a new customer is added or when an order is shipped.
• Benefits
  • Real-time event notifications, allowing for more immediate and responsive workflows.
  • Lightweight and simple to implement, requiring only a URL to be registered and a notification payload to be sent.
  • Highly customizable, allowing developers to specify which events to receive notifications for and how to process them.
  • WReliable way to receive notifications, as they are delivered over HTTP and can be retried if delivery fails.
• Costs
  • API provider responsible for failures and retries.
  • Security measures like firewalls may block webhooks.
  • Many events in a burst may cause a webhook to fail or extra complexity.
  • It may be difficult to rewind evens from a webhook if it fails.

Web Sockets

• Web sockets provide a persistent, bi-directional communication channel between a client and server over a single TCP connection.
• With web sockets, a client can send and receive real-time data without the need for repeated HTTP requests and responses.
• Web sockets can be used for a wide range of use cases, such as chat applications or real-time data visualization.
• Benefits:
  • Real-time, low-latency communication, allowing for highly responsive applications.
  • Single TCP connection, reducing the overhead and complexity of managing multiple connections.
  • Full-duplex communication, allowing data to be sent and received simultaneously.
  • Highly scalable, as they can handle large numbers of concurrent connections.
• Costs:
  • Client must maintain a persistent connection, which can be difficult to manage or have less reliability.
  • Scaling web sockets can be difficult, as they require a single connection per client.
  • Same-origin policy, which prevents web sockets from being used across domains.

HTTP Streaming

• HTTP streaming is a mechanism for sending real-time data from a server to a client over HTTP.
• With HTTP streaming, a server can send data to a client in real-time without the need for repeated HTTP requests and responses.
• HTTP streaming can be used for a wide range of use cases, such as real-time data feeds or stock tickers.
• Chunked transfer encoding is a mechanism for sending data in chunks over HTTP.
• Server-sent events (SSEs) are a mechanism for sending real-time data from a server to a client over HTTP.
• Use by Twitter for example for messaging updates.
• Benefits:
  • Provides real-time data delivery, allowing for more immediate and responsive workflows.
  • Single HTTP connection, reducing the overhead and complexity of managing multiple connections.
  • Full-duplex communication, allowing data to be sent and received simultaneously.
  • Highly scalable, as it can handle large numbers of concurrent connections.
• Costs
  • Bidirectional communication requires a persistent connection, which can be difficult to manage or have less reliability.
  • Buffering can cause delays in data delivery.

General API Development Checklist

• Establish clear, consistent naming conventions
• Avoid overcomplicating the API
• Implement versioning
• Handle errors properly
• Consistently handle authentication and authorization
• Provide adequate documentation
• Provide appropriate amount of data
• Design API for scalability
• Consider performance
• Provide appropriate security measures

API Gateway Development Checklist

• Implement caching
• Configure throttling and quotas
• Implement appropriate authentication and authorization
• Keep API design simple
• Handle errors properly
• Design API for scalability
• Consider performance when designing API
• Provide adequate documentation
• Version API
• Secure API
• Handle Cross-Origin Resource Sharing (CORS)
• Validate user input
• Avoid over-reliance on API Gateway features
• Monitor and log API
• Manage access and permissions