Have you ever wondered about all the different kinds of APIs underlying the apps and services you use everyday? As an experienced tech specialist, I‘ll provide you an insider‘s overview into the major API categories that power modern software applications.
We‘ll examine the most popular API types based on who can access them and how they are architected. Read on to gain clarity on making the optimal API choice for your next project!
An API Taxonomy: A 10,000 Foot View
Before we dive deeper, let‘s briefly characterize the API landscape by two key perspectives:
Accessibility: Who is allowed to use the API?
- Public/Open
- Private/Internal
- Partner/External
Architecture: How is the API technically designed?
- REST
- SOAP
- GraphQL
- RPC
Understanding where an API falls along these two dimensions provides initial insight into its capabilities and use cases. Now let‘s explore each category more thoroughly.
Public APIs: Innovation Catalysts
Public or open APIs allow universal access to developers looking to integrate with and build upon external platforms. Prominent examples include:
- Twitter API: Enables creation of client apps leveraging Twitter‘s core capabilities
- Google Maps API: Allows embedding interactive maps in external sites and apps
- Spotify API: Allows developers to tap into Spotify‘s music data and metadata
These APIs spur innovation by supplying open interfaces to extensive capabilities and datasets. However, with great power comes great responsibility! Public API providers must consider:
Rate Limiting: Prevent traffic spikes from crippling availability
Security: Most public APIs now employ OAuth access control policies
Let‘s examine public API adoption trends:
| Year | Total Public APIs | New Public APIs Added |
|---|---|---|
| 2015 | 14,525 | 1,452 |
| 2018 | 22,752 | 1,741 |
| 2021 | 29,989 | 2,237 |
Statistics Source: ProgrammableWeb
The growth shows no signs of stopping with public APIs more than doubling in six years! Their open access enables groundbreaking integrations, fueled by API consumers demanding innovative data mashups.
You too can leverage public APIs instead of reinventing the wheel for common capabilities like maps, payments, logins etc. The flip side? You must manage spikes, security risks and dependency risks if a provider API goes down!
Private APIs: Oasis of Control
Now let‘s enter restricted access territory with private or internal APIs. Unlike public APIs, these are exclusively used within an organization‘s developer teams to enable internal systems integration. Teams use private APIs to tap into in-house datasets and services securely.
For instance, Netflix has an extensive internal API ecosystem that allows services to share critical business data while preventing external exposure. Some common private API use cases include:
- Cross-team data sharing: Enable discoverability and reuse of proprietary datasets
- Legacy system integration: Safely expose legacy system capabilities to modern apps and microservices
- Automating workflows: Allow programmatic control and orchestration of internal business processes
The main value private APIs provide is centralized access control. Core business logic and data remains invisible to the outside world. However, they can impose significant governance overhead regarding access policies, rate limits etc.
Private APIs have allowed companies like Netflix to create unified cross-functional platforms internally while maintaining stringent external security.
Partner APIs: Controlled Collaboration
We‘ve seen open access on one end and locked-down private access on the other end of the API access spectrum. Partner APIs occupy the middle ground – they allow programmatic access to external entities, but only to verified partners.
Exposing APIs to select partner groups allows providers to reap joint value. API consumers reciprocate by delivering integrated offerings that expand customer reach for providers.
For example, Stripe furnishes payment APIs to platform partners like Shopify, Wix etc. By integrating Stripe‘s payment processing into their offerings, Stripe‘s partners can enable smooth transactions for end-customers.
Some common partner API use cases include:
- Cloud services firms exposing APIs to Managed Service Providers (MSPs) to manage customer infrastructure
- Retailers providing APIs for value-added integrators to build complementary purchasing experiences embedded in partner channels
A major risk of partner programs is unravelling the intricate balance between API program commercialization and adequate partner support. Without robust partner developer portals, hands-on guidance, and self-service access policies, partner API initiatives flounder.
If cultivated effectively though, such symbiotic platform ecosystems can enable breakthrough value creation and reach.
Composite APIs: United We Stand
We‘ve covered various access control models so far – but what happens when you need aggregated access to multiple internal and external APIs? Enter composite APIs.
A composite API essentially acts as an orchestration intermediary layer invoking multiple discrete APIs and aggregating their data into unified responses. Composite APIs allow simpler unified access to diverse business capabilities through a consolidated façade gateway.
For example, Google Maps provides a composite API combining:
- Maps data API for geospatial visualizations
- Places API bringing in business and attraction data
- Routes API for navigation
- Geocoding API for coordinate conversions
This enables fully fledged location-aware app experiences via single API rather than integrating the distinct APIs separately.
Composite APIs are tremendously powerful integration hubs. However, they also pose elevated uptime and performance risks due to their dependency on numerous backing APIs and services. If certain constituent APIs slow down or fail, your entire composite API can grind to a halt!
Increasing adoption of microservices architectures further elevate the need for composite APIs to aggregate their disparate capabilities into full-stack client experiences.
API Architecture Styles: Functionality Pedestals
We‘ve covered various API access policies so far. Now let‘s switch gears to drill down on API categories based on how they are architected. The architectural choices dictate the overall functionality and performance profile for target applications.
We‘ll provide an overview of prominent styles like REST, SOAP, GraphQL etc. Let‘s decode their distinctions!
REST – Ubiquitous Data Services
REST (Representational State Transfer) has overwhelmingly become the standard for API architectural style, especially for web APIs. Core REST concepts include:
- Exposing discrete resources with identifiers, metadata, and actions
- Leveraging HTTP methods like GET, POST, PUT, DELETE to manipulate resources
- Responses using widely compatible formats like JSON and XML
- Stateless client-server interaction
This principles-driven architectural approach has made REST incredibly interoperable. The ubiquity of REST across devices, apps, and infrastructure has cemented its popularity.
Adoption statistics affirm the dominance of REST:
- Over 70% of public cloud application APIs are REST-based
- The most common API performance issue reported by Cisco is not having a REST API available!
However, while immensely versatile, REST APIs also face over-fetching and under-fetching data issues without efficient querying mechanisms. Complex nested hierarchies can be cumbersome to model RESTfully.
SOAP – Strict Enterprise Contracts
SOAP (Simple Object Access Protocol) is an XML-based messaging protocol for more formalized machine-to-machine communication. Core aspects include:
- Rigorously defined operations and schema contracts
- XML message payloads providing validation
- Built-in support for security and transactions
- Underlying protocol agnostic so that APIs can use SMTP, FTP etc. besides HTTP
These XML-powered contracts enable guaranteed precision by validating inputs and outputs – crucial for sensitive enterprise systems. However, the resultant verbosity hampers efficiency and learner-friendliness.
Public cloud adoption has diminished SOAP usage given heavier resource demands compared to REST. However, many legacy enterprise systems and specialized verticals like finance still rely heavily on SOAP APIs.
GraphQL – Evolving Request Flexibility
GraphQL, popularized by Facebook, offers an alternative API interaction model focused on descriptive querying. Key attributes:
- Clients specify nested data requirements in queries
- Strongly typed schemas define what queries are permissible
- Real-timeRESOLUTION data fetching
- Hierarchical data modeling
For example, retrieving actor details with related movies in one request avoids round-trips. The strict schema enables superior developer tooling, documentation, and code generation.
However, GraphQL‘s flexibility does impose a learning curve. Query complexity also necessitates matching compute resources, security policies and caching mechanisms to prevent overload.
GraphQL is gaining strong traction for mobile, web and IoT apps needing customizable data. Apollo GraphQL boasts over 26 million downloads of its framework to simplify adoption.
RPC – Reusable Abstractions
RPC (Remote Procedure Call) APIs focus on executing named procedures and functions rather than just CRUD operations. Core traits:
- Centered around calling remote methods like local functions
- Underlying protocol depends – gRPC uses HTTP/2, Apache Thrift can use raw TCP
- Optimization for internal microservices vs. external consumption
For example, transcoding video files in multiple qualities can be wrapped in aEncodeVideo RPC API instead of needing explicit quality parameters.
Encapsulating complex application logic behind procedure calls allows simpler integration. However, ubiquitous connectivity across diverse endpoints may require REST APIs as an interoperable façade.
RPC APIs are immensely popular for efficient internal microservices integration, with gRPC usage growing over 350% from 2020 to 2021 as per SlashData.
Key API Architecture Comparison
| Type | Data Format | Contracts | Transports | Strengths | Weaknesses |
|---|---|---|---|---|---|
| REST | JSON, XML | None | HTTP | Ubiquitous | Verbosity |
| SOAP | XML | WSDL | HTTP, SMTP etc. | Validation | Overhead |
| GraphQL | JSON | Schema | HTTP | Flexibility | Learning curve |
| RPC | Protocol Buffers etc. | Interface definitions | gRPC, Thrift protocols | Efficient | Language dependencies |
This comparison summarizes how architectural choices align to API use case needs regarding data formats, transports, integration flexibility etc.
Matching API Type to Application Requirements
We‘ve covered a variety of API species in their natural habitats! Here is holistic guidance on which API types are best fit for your needs:
You Need Open Innovation Ecosystems
Public APIs fuel external developer communities. Want to enable next-generation video experiences? Expose editing and streaming capabilities.
Seeking Unified Internal Access?
Implement internal APIs for publishing centralized libraries of proprietary data and services.
Have Trusted External Partners?
Partner APIs allow sharing capabilities while protecting intellectual property through access policies.
Support Diverse Client Experiences?
Composite APIs aggregate backend microservices into full-stack facades like e-commerce.
Need Ubiquitous Mobile/Web Access?
Build RESTful interfaces for interoperable resource-based data exchange.
Complex Enterprise Integrations?
Leverage SOAP APIs for standardized XML contracts and built-in compliance.
Customizable Real-Time Data Queries?
Provide GraphQL endpoints for fluid queries within schema boundaries.
Reuse Encapsulated Business Logic?
Expose core complex workflows as RPC procedure interfaces.
This checklist encompasses the spectrum spanning open communities to internal microservices. Analyze integration needs, security constraints, use cases and capacity planning demands to choose appropriately.
An API for Every Need Awaits!
We‘ve undertaken an extensive learning journey across API classification dimensions, diving into public APIs fueling innovation through to RPC interfaces abstracting internal logic.
Key insights include:
- Public exposure tradeoffs between extensibility and risk management
- Private APIs enable centralized data control but require governance
- Partner programs walk the tightrope between commercialization and support
- Composite APIs simplify access but pose concentrated failure risks
- REST dominates external-facing APIs while RPCs lead internal microservices integration
- GraphQL offers evolved data querying capabilities
You‘re now equipped to make discerning API choices by asking:
- Who needs access – external developers, partners or just internal teams?
- What functionality lies beneath – data aggregation or business workflows?
- What scale and performance is expected?
- What are the adjacent reliability, security and support needs?
Answering these critical questions will unveil the most appropriate API approach for your application goals!
