Asynchronous APIs: What Are the Benefits? | Dreamfactory

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If you have worked mainly with REST APIs, there's a chance you might not be acquainted with asynchronous APIs and their protocols, such as WebSockets, Kafka, and AMQP. Asynchronous APIs enable you to manage multiple requests simultaneously to communicate between services effectively.

Many similar tasks can be performed using both these APIs; however, some use cases can be managed better with a particular API. Let’s delve deeper into the difference between synchronous and asynchronous APIs.

Here's the key things to know about asynchronous APIs:

    • Synchronous APIs provide instant responses; asynchronous APIs use callbacks.

    • Synchronous requests are sequential, leading to delays; asynchronous enables parallel processing.

    • Event-driven architecture enhances real-time experience and efficiency.

    • Asynchronous APIs return calls instantly and process in the background.

    • Different messaging protocols (WebSockets, Webhooks, SSE) offer real-time solutions.

The Difference Between Synchronous and Asynchronous APIs

Both synchronous and asynchronous application programming interfaces function by returning data requests. The significant difference is that synchronous APIs provide requests for data and services immediately. In contrast, their asynchronous counterparts give a callback to the requester as soon as the request is ready.

However, in the case of synchronous APIs, the requests happen sequentially, and with every interaction, the process gets blocked until it is complete. It implies that the response time to the client using the application is a sum of the response times of each microservice provided by the app.  Another drawback of synchronous APIs is that if a user wants an update, the API needs to be invoked continuously to look for data modifications.  

Making APIs event-driven or asynchronous can solve these bottlenecks and enhance the real-time experience.  Moreover, employing an event-driven architecture has significant benefits, including a great user experience and increased system efficiency.

Asynchronous APIs work by returning the API calls instantaneously with a polling URL while the asynchronous request continues to be processed in the background. It ensures that the functionality of an application is maintained, thereby keeping the app resources free to process newer requests. 

Moreover, synchronous APIs work best in places with higher connectivity and low latency. If the connectivity is lacking or oversaturated, it is best to use asynchronous APIs. Also, when some of your API requests have a longer execution time, it is good to consider expensive operations outside the request. So, the responses to these requests can be provided faster.  

For instance, a REST API operation sometimes takes a lot of time to process. Rather than keeping the client waiting for the operation's completion, it is best to return an instantaneous response and process the request later.

Using AsyncAPI to Define Event-Driven APIs

An AsyncAPI is an open-source tool that enables you to describe event-driven architectures and document asynchronous applications in a format that is machine-readable.

The elements of AsyncAPI are similar to an OpenAPI, but it has some additional features regarding the accommodation of an event. It supports many messaging protocols and transports, including WebSockets, Kafka, STOMP, JMA, AMQP, MQTT, and HTTP, along with event schema format. 

So, when you define an event-driven architecture with AsyncAPI, it includes the event payload definition, name of the channel, protocols, application headers, and other eventing semantics.

What Are Asynchronous Messaging Protocols for APIs?


A webhook can be considered a type of API that operates on events. This service enables data transfer from one program to another when an event occurs. So, there is no specification regarding the request from your server other than the confirmation of receipt. 

These are also known as reverse APIs, as the app that sends data is initiating the communication rather than receiving the data. With the increased interconnectedness of web services, webhooks are being used as a more straightforward solution to enable data updates and push notifications to one or more endpoints in real time, and that too without using a robust API solution. 


This protocol ensures that the server and the client can have two-way communication. It implies that both entities can share information as and when required. WebSockets enable you to send messages to a server and get event-driven responses without polling the server for a response.  

WebSockets do not have a point-to-point connection or any pub-sub support. 

GraphQL subscriptions

GraphQL is a query language used for APIs. You can carry out asynchronous communications from a GraphQL server through live queries and subscriptions. If you are looking forward to adding real-time functionalities to an app powered by GraphQL, then subscriptions are the key. For instance, the live comments and streaming reactions feature on Facebook were made possible because of GraphQL subscriptions developed internally by the company. 

Live queries were created later and are not as widely used. Also, they are not yet a part of the GraphQL subscription. The main difference between a subscription and a query is that subscriptions are used to observe events, whereas live queries are employed for observing data. 

The GraphQL subscriptions are inbuilt in GraphQL and enable asynchronous and synchronous interactions through a single API experience. So, a single API can support both request-response commands and queries as well as asynchronous event-based notifications. 

Server-sent events

Standard request-response interactions send HTTP requests to the server as soon as the client opens the connection. It then gets an HTTP response, and the connection is closed upon completion of the interaction. So, this scenario always takes place when a client requests data.   On the other hand, Server-Sent Events (SSE) enable the data to be pushed by the server asynchronously as soon as the client opens the client-server connection. As soon as the client establishes a connection, the server provides the data and transfers it to the client whenever any new data event occurs. So, this process has acquired the name Server-Sent-Events.

What Are Some Practical Use Cases of Asynchronous APIs?

Whether it is social media or other sectors such as banking or gaming, asynchronous APIs are being used widely to boost application performance and improve responsiveness.


Billions of people worldwide use the messaging feature of apps such as Facebook, Instagram, and WhatsApp to stay connected. Therefore, there are a large number of user interactions that these apps have to process.

These apps use asynchronous APIs to process the numerous parallel requests in the background without requiring users to wait for a response. Many of these async requests do not need to be processed simultaneously—for instance, a post from a friend or a notification regarding a message.

Additionally, some of these may need to be processed faster. Facebook uses Async to manage these types of asynchronous requests, which handles billions of requests efficiently.


Asynchronous transactions are common in banking, where credit transactions are made frequently. These transactions are managed by a processor that functions as a mediator between the merchant and the bank.

Customers make payments through the website hosted by the processor. The merchant initiates the transaction, and the server returns the response later. If the customer abandons a transaction, the server does not send a response.

Asynchronous APIs in credit transactions act as a single point of entry for different processors requiring the customer to provide payment details on the payment site hosted by the bank. As soon as the transaction is initiated, the merchant provides a bank identifier for the bank that will process the transaction.


Asynchronous multiplayer games have been a huge success recently. These allow you to play against friends and other people without real-time data exchange.

Asynchronous multiplayer games are widely used on mobile platforms, and they employ asynchronous APIs since the game is frequently interrupted because players are busy with other activities.

Handling Security and Authentication in Asynchronous APIs

In the rapidly evolving landscape of modern application development, security and authentication remain paramount concerns. Asynchronous APIs, with their ability to facilitate real-time communication and data exchange, introduce new challenges and considerations when it comes to ensuring the privacy and integrity of transmitted information. In this section, we will delve into the strategies and best practices for effectively handling security and authentication in asynchronous APIs.

1. Token-Based Authentication for Asynchronous APIs

Token-based authentication is a widely adopted method for securing APIs, including asynchronous ones. It involves the exchange of tokens between the client and server to validate and authorize requests. The process typically consists of the following steps:

    • Authentication Request: The client sends a request containing user credentials (such as username and password) to the server.

    • Token Generation: If the credentials are valid, the server generates a token (often a JSON Web Token or JWT) and sends it back to the client.

    • Token Storage: The client stores the received token securely, often in local storage or cookies.

    • Token Inclusion: For every subsequent request to the server, the client includes the token in the request headers.

    • Server Validation: The server verifies the authenticity and validity of the token before processing the request.

Token-based authentication provides several benefits for asynchronous APIs. It enables stateless communication, allowing servers to scale easily and ensuring that requests can be handled by any server in a distributed environment.

2. OAuth for Enhanced Security

OAuth (Open Authorization) is a robust framework that provides secure authentication and authorization for both synchronous and asynchronous APIs. It allows third-party applications to access user data without exposing sensitive credentials. OAuth is commonly used in scenarios where users grant permissions to external applications, such as social media logins or accessing resources from different services.

OAuth 2.0, the current version of the framework, employs tokens for authentication and supports different grant types, including Authorization Code, Implicit, Resource Owner Password Credentials, and Client Credentials. By implementing OAuth, asynchronous APIs can offer a seamless user experience while maintaining stringent security standards.

3. Role-Based Access Control (RBAC)

In an event-driven architecture facilitated by asynchronous APIs, it's crucial to enforce role-based access control. RBAC ensures that only authorized users or components can access specific events, channels, or resources. By assigning roles and permissions, developers can dictate who can publish, subscribe to, or perform actions on events.

Implementing RBAC in asynchronous APIs helps prevent unauthorized access to sensitive data and actions, safeguarding the integrity of the system and maintaining user privacy.

4. Secure Connection Protocols

Security starts at the transport layer. When setting up communication channels for asynchronous APIs, it's essential to use secure connection protocols such as HTTPS and WSS (WebSocket Secure). These protocols encrypt data during transmission, preventing eavesdropping and data interception by malicious actors.

5. Monitoring and Auditing

Continuous monitoring and auditing are indispensable components of a robust security strategy for asynchronous APIs. Implementing logging mechanisms to track events, errors, and access attempts helps identify suspicious activities and potential security breaches. By analyzing logs, developers can take proactive measures to rectify vulnerabilities and enhance security protocols.

Final Thoughts

Using asynchronous APIs has many benefits, such as enhanced responsiveness and improved communication.

Moreover, in the wake of increasing interconnectedness and complexities in applications, asynchronous APIs are here to stay. However, it is essential to know when to use them and when they cannot replace their synchronous counterparts. Professional developers understand that both these APIs have unique benefits, and they may even use a hybrid architecture to improve communication within the app.

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Frequently Asked Questions: Asynchronous APIs

What are asynchronous APIs, and how do they differ from REST APIs?

Asynchronous APIs enable simultaneous handling of multiple requests for effective communication between services. Unlike REST APIs, which provide immediate responses, asynchronous APIs use callbacks to notify requesters when the data is ready.

Why might someone choose asynchronous APIs over synchronous ones?

Asynchronous APIs solve issues with sequential requests in synchronous APIs. They prevent blocking processes, enhance real-time experiences, and maintain application resources by processing requests in the background.

How do synchronous APIs affect response times and user experience?

Synchronous APIs execute requests sequentially, leading to increased response times for each microservice. They require continuous invocation for updates and can create delays in user experience.

What are the benefits of using an event-driven architecture with asynchronous APIs?

Employing an event-driven architecture through asynchronous APIs improves user experience and system efficiency. Real-time updates and responsive applications are achieved while freeing up resources for newer requests.

When is it best to use synchronous APIs, and when are asynchronous APIs more suitable?

Synchronous APIs are ideal for high connectivity and low latency scenarios. Asynchronous APIs are preferred when connectivity is lacking, oversaturated, or when dealing with longer execution times for certain requests.

How does the AsyncAPI tool contribute to event-driven architectures?

AsyncAPI is an open-source tool for describing and documenting event-driven architectures in a machine-readable format. It accommodates various messaging protocols such as WebSockets, Kafka, and AMQP, along with event schema formats.

What practical applications benefit from asynchronous APIs?

Asynchronous APIs are widely used in messaging apps like Facebook and banking transactions for improved performance. They are also essential for asynchronous multiplayer gaming, enabling gameplay without real-time data exchange.