All Differences Between Stateless VS Stateful API

When web developers are designing their applications, a lot of factors have to be accounted for. APIs (Application Programming Interfaces) are one of many variables that constitute a functioning app. However, there are different classifications of APIs, one of them based on how they retain information. These APIs are separated into two types: stateless and stateful APIs.

One of the most popular API architecture styles falls into one of the two categories between stateful and stateless APIs - the RESTful (Representational State Transfer) API. If you are not sure which classification of state RESTful APIs fall into, give this article a read:

REST API vs. RESTful API: What’s the Difference?

Confused by REST and RESTful APIs? This deep dive clarifies their nuances, from core principles to key differences. Discover why “strictly RESTful” reigns supreme.

Apidog BlogHabibur Rahman

What Are Stateless APIs?

Stateless APIs are APIs that treat each request from a client to a server as an independent transaction, and also where the server does not retain any information about the client's previous interaction.

Key Characteristics of Stateless APIs

1. Independence of Requests: Each request sent from a client to the server contains all the necessary information for the server to process it, and is not affected by any prior requests made, nor affects any requests in the future.
2. No Session Management: Stateless APIs do not require the server to manage client sessions or store any session-related data. As a result, there is no need for session tracking mechanisms such as cookies or server-side sessions.
3. Scalability: Stateless APIs are highly scalable because servers can process requests independently without the need to maintain client state. Load balancers can distribute incoming requests across multiple servers without concern for session affinity.
4. Simplicity: Stateless APIs are generally simpler to implement and understand compared to stateful APIs. Since each request contains all the necessary information, there is no need for complex session management or state synchronization between the client and server.
5. Fault Tolerance: Stateless APIs are inherently fault-tolerant because servers do not rely on maintaining client state. If a server fails, incoming requests can be routed to other servers without any impact on client interactions.

Advantages of Stateless APIs

1. Flexibility: Stateless APIs provide flexibility in scaling and deployment. Since servers do not maintain a client state, new server instances can be added or removed from the pool without impacting client interactions. This flexibility allows for dynamic scaling based on demand and enables efficient resource utilization in cloud environments.
2. Performance: Stateless APIs often offer better performance compared to stateful APIs. Since each request contains all the necessary information for processing, servers can respond quickly without the overhead of managing the session state or performing additional lookups. This results in lower latency and faster response times, especially under heavy load conditions.

Disadvantages of Stateless APIs

1. Difficulty in Implementing Complex Workflows: Stateless APIs may struggle to handle complex workflows or transactional processes that require maintaining state between multiple requests. Implementing features such as multi-step transactions or long-running processes may be more challenging with stateless APIs compared to stateful alternatives.
2. Limited Support for Real-Time Interactions: Stateless APIs are primarily designed for request-response interactions and may not be well-suited for real-time communication or collaboration scenarios. Implementing features such as real-time updates or notifications may require additional workarounds or compromises.

Examples of Popular Stateless APIs

1. RESTful APIs: Representational State Transfer (REST) is an architectural style for designing networked applications. RESTful APIs are stateless by design, where each request from a client to the server contains all the necessary information for the server to process it. Examples of RESTful APIs include those provided by social media platforms like Twitter and Facebook, e-commerce platforms like Amazon, and cloud services like AWS (Amazon Web Services) and Azure.
2. HTTP APIs: Hypertext Transfer Protocol (HTTP) APIs follow the principles of statelessness, where each HTTP request is independent and self-contained. These APIs are commonly used for communication between web clients (such as browsers or mobile apps) and web servers. Examples include public APIs provided by services like Google Maps, OpenWeatherMap, and GitHub.
3. GraphQL APIs: GraphQL is a query language for APIs that enables clients to request only the data they need. While GraphQL itself is agnostic to statefulness, it's often implemented in a stateless manner over HTTP. GraphQL APIs typically expose a single endpoint for executing queries, mutations, and subscriptions, with each request containing the specific data requirements. Examples of GraphQL APIs include those provided by GitHub, Shopify, and Yelp.
4. Microservices APIs: Microservices architecture decomposes complex applications into smaller, independently deployable services. Each microservice can expose its API, typically implemented as stateless APIs using protocols like HTTP or gRPC. Examples of microservices APIs include those used by Netflix for streaming, Uber for ride-hailing, and Spotify for music streaming.
5. Serverless APIs: Serverless computing platforms like AWS Lambda and Google Cloud Functions enable developers to deploy code without managing servers. Serverless APIs are often implemented as stateless functions triggered by HTTP requests or other events. These APIs are ideal for lightweight, event-driven applications and backend services. Examples include serverless APIs for processing user uploads, sending notifications, and performing data processing tasks.

What are Stateful APIs?

Stateful APIs are APIs that maintain the state or context of client interaction with servers between requests. This is the exact opposite of what stateless APIs are - stateful APIs can keep track of resources, and process subsequent requests that derive from the same client.

Key Characteristics of Stateful APIs

1. Session-Based Security: Stateful APIs offer robust session-based security mechanisms for authenticating and authorizing clients. By establishing sessions with clients and managing session tokens or cookies, these APIs can enforce access controls, permissions, and security policies consistently across multiple requests.
2. Consistency and Reliability: Stateful APIs ensure consistency and reliability by synchronizing client state between the client and server. This helps prevent data inconsistencies, race conditions, and concurrency issues that may arise in distributed systems with shared states or resources.
3. Efficient Resource Utilization: Stateful APIs can optimize resource utilization by reusing established sessions or connections between the client and server. This reduces the overhead of repeatedly authenticating and establishing connections for each request, resulting in improved performance and reduced network latency.
4. Real-Time Updates: Stateful APIs facilitate real-time communication and updates between clients and servers by maintaining continuous connections. This allows servers to push updates, notifications, or data changes to clients instantly, enabling real-time collaboration, messaging, and streaming applications.
5. Contextual Insights: Stateful APIs enable servers to gain contextual insights into client behavior, preferences, and usage patterns over time. By analyzing session data and client interactions, applications can derive valuable insights for personalization, optimization, and decision-making.

Advantages of Stateful APIs

1. Session Management: Stateful APIs allow for the establishment and management of sessions between clients and servers. This enables the server to maintain client context and state between requests, which can be beneficial for applications that require continuous interactions and personalized experiences.
2. Complex Business Logic: Stateful APIs are well-suited for applications with complex business logic or workflows that require maintaining context across multiple requests. The server can maintain the state of long-running transactions, workflows, or state machines, enabling more efficient processing and coordination.

Disadvantages of Stateful APIs

1. Concurrency Issues: Managing concurrent access to shared state can be challenging in stateful APIs. Race conditions, data inconsistencies, and concurrency issues may arise when multiple clients access or modify shared resources concurrently, requiring careful synchronization and locking mechanisms to ensure data integrity.
2. Difficulty in Horizontal Scaling: Stateful APIs may face challenges in horizontally scaling across multiple server instances due to the need to maintain session state. Distributing sessions across multiple servers and ensuring consistency and synchronization between them can be complex and may require additional infrastructure or middleware.

Examples of Popular Stateful APIs

1. WebSocket APIs: WebSocket is a communication protocol that provides full-duplex communication channels over a single TCP connection. WebSocket APIs maintain persistent connections between clients and servers, allowing for real-time bidirectional communication. They are commonly used in applications that require instant messaging, online gaming, collaborative editing, live updates, and other real-time interactions.
2. Remote Procedure Call (RPC) APIs: RPC APIs enable clients to invoke procedures or methods on a remote server and receive responses. While RPC itself is agnostic to statefulness, some implementations maintain client state between requests, especially in cases where sessions or connections are long-lived. RPC APIs are commonly used in distributed systems, microservices architectures, and client-server applications.
3. Session-based APIs: Some legacy APIs rely on session-based authentication and maintain client state using mechanisms like cookies or session tokens. These APIs require clients to authenticate and establish a session with the server, and the server maintains the session state for the duration of the session. Session-based APIs are commonly used in web applications, e-commerce platforms, and enterprise systems.
4. Real-time Data Streaming APIs: Real-time data streaming APIs maintain persistent connections between clients and servers to stream data in real time. These APIs are commonly used in applications that require continuous data updates, such as financial trading platforms, IoT (Internet of Things) systems, real-time analytics, and monitoring dashboards.
5. Collaborative Applications: Collaborative applications, such as collaborative document editing platforms, collaborative drawing tools, and collaborative project management tools, often use stateful APIs to enable real-time collaboration among multiple users. These APIs maintain a shared state between clients and servers, allowing users to see each other's changes in real-time.

Coding Differences Between Stateless VS. Stateful APIs

The coding example will involve utilizing the Python Flask web framework. Notice that there is an extra session library implemented in the stateful API coding.

Stateless APIs:

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/stateless', methods=['GET'])
def stateless_endpoint():
    # Get data from request
    data = request.args.get('data')
    
    # Process the request (e.g., perform a calculation)
    result = int(data) * 2
    
    # Return the result
    return jsonify({'result': result})

if __name__ == '__main__':
    app.run(debug=True)

Stateful API:

from flask import Flask, request, jsonify, session

app = Flask(__name__)
app.secret_key = 'your_secret_key'  # Secret key for session management

@app.route('/stateful', methods=['GET'])
def stateful_endpoint():
    # Get data from request
    data = request.args.get('data')
    
    # Check if session exists
    if 'result' in session:
        # If session exists, update the result with new data
        session['result'] += int(data)
    else:
        # If session doesn't exist, initialize the result with data
        session['result'] = int(data)
    
    # Return the current result stored in the session
    return jsonify({'result': session['result']})

if __name__ == '__main__':
    app.run(debug=True)

Comparison:

• The stateless API code example only takes the query parameter's data and performs the code's operation, followed by returning the result as JSON.
• In the stateful API code example, the query parameter's data, and saves the value suing Flask's session management. The store valued can then be used in the same client session, updating it every time a request is made.

Tabulated Summary of the Comparison Between Stateless VS. Stateful APIs

Apidog - Perfecting your Stateless and Stateful APIs

To develop useful APIs for other developers to implement into their applications, you will need a proper API tool to support your API development processes. We recommend Apidog, an all-in-one API development platform that can support developers with functionalities for the entire API lifecycle.

Initializing Design for a New API with Apidog

With Apidog, creating a new API is just within a few clicks and fingertips!

Firstly, click the New API button to start creating a new API.

Next, you can choose the necessary characteristics of your new API. You can choose the corresponding HTTP method, craft your own API endpoint (or API URL), and provide any relevant parameters and description that you think may be useful for you and other developers who may utilize your API.

After creating your very first API on Apidog, you can continue testing your APIs! Yes, Apidog facilitates testing, debugging, and also documenting features, so you do not need to export your files just to test whether your API is functional or not!

Testing APIs using the Testing Scenario Function on Apidog

Firstly, hit the Testing button, followed by the + New Test Scenario button.

Apidog will prompt you to fill in the details for your new test scenario. Make sure to give it a proper name so its function is predictable.

Continue by adding a step (or many more steps) to your test scenarios by clicking on the Add Step section. You should be able to see the image below.

Select "Import from API" from the drop-down menu.

Next, select all the APIs you would like to include in your test scenario. In the example above, the API called NumberConversionSOAP has been included.

Before hitting the Run button to start your test scenario, make sure to change the test scenario environment, which should be Testing Env, as pointed out by Arrow 1.

With Apidog, you can enjoy concise and detailed analyses for your testing scenarios. Using the statistics, you can decide which part of the API needs further refinement, and which parts you have done perfectly!

Conclusion

The choice between stateless and stateful APIs really depends on the specific requirements of the application and the trade-offs involved, as they are not a one-for-all solution to web development problems.

The main takeaway that you should understand is that both stateless and stateful APIs excel when certain conditions are met.

Stateless APIs are commonly used in distributed systems and microservice architectures, where data is sent and requests are independent from one another.

Stateful APIs are suitable for applications that require clients to have a constant connection with the server, such as live video streams and online collaborative applications.

Unlike stateful and stateless APIs, Apidog is an all-in-one API tool for developers who wish to create, modify, and maintain APIs. With the facilitation of all necessary functionalities and specifications for the entire API lifecycle, developers can rely on Apidog to provide them with the services required to produce the best quality APIs.