Decoding WhatsApp's Backend: The Role of Erlang and Other Technologies

WhatsApp, with over 2 billion active users worldwide, is a messaging app that has become an integral part of daily communication. While it is often said that WhatsApp is written in Erlang, the reality is more nuanced. This article delves into the intricacies of WhatsApp's backend architecture and the role that Erlang plays, along with other essential technologies that contribute to its performance and reliability.

Erlang: A Key Technology in WhatsApp's Backend

No, WhatsApp is not fully written in Erlang. However, a significant portion of its backend is indeed developed using Erlang, particularly for handling its vast number of concurrent connections and messages. Erlang is renowned for its capability to build scalable and fault-tolerant systems, making it an excellent choice for WhatsApp's communication needs.

Erlang is an actor model-based language that excels in managing large-scale, distributed systems. It is designed to handle concurrency in a highly efficient manner, making it ideal for an app like WhatsApp which needs to manage billions of connections and messages simultaneously. Additionally, Erlang's fault tolerance and distribution capabilities ensure that the system can recover quickly from failures and maintain high availability.

Other Technologies and Languages in WhatsApp's Arsenal

While Erlang is central to WhatsApp's backend, the app relies on a combination of technologies and languages for various components of its infrastructure. For instance, C and Java are used for different parts of WhatsApp's server and client-side functionalities. This mixed approach allows WhatsApp to leverage the strengths of multiple technologies, thereby enhancing the overall performance and reliability of its messaging service.

Backend Infrastructure

The backend systems that handle message routing and other critical functionalities are predominantly implemented in Erlang. This choice is justified by the language's ability to handle high throughput and distributed systems efficiently. Additionally, WhatsApp has contributed to the development of the Ejabberd, an open-source Jabber server written in Erlang, further emphasizing its commitment to this technology.

Server-Side Technologies

The server-side infrastructure of WhatsApp is built on several technologies, including:

Erlang BEAM: The BEAM virtual machine (VM) is the runtime environment for Erlang and Elixir languages. It provides a high-performance execution environment with automatic memory management and built-in concurrency support. FreeBSD: WhatsApp uses FreeBSD as the underlying operating system, known for its stability and reliability, which are crucial for handling high traffic and maintaining system performance. Yaws, lighttpd, and PHP: These web servers and scripting languages are used for serving static content and managing web-based services. Custom Patches to BEAM: WhatsApp has made custom modifications to the BEAM VM to optimize performance and meet the specific requirements of the app.

The hosting for these backend systems is primarily done on SoftLayer, a cloud-based infrastructure provider, which ensures that the servers are always up and running, even under heavy load.

Frontend and Protocol Evolution

The frontend of WhatsApp is developed for multiple platforms, including:

iPhone Android BlackBerry Nokia Symbian S60 and S40 Windows Phone

The app uses SQLite for local database management and synchronization, ensuring that users can access their messages even when offline.

It is worth noting that WhatsApp has internally developed its own protocol to replace XMPP. This protocol restructuring and incorporation of changes into the Erlang VM have contributed significantly to achieving optimal server performance and enhanced security.

Conclusion: The Nuance of WhatsApp's Backend

While it is reasonable to assume that a substantial portion of WhatsApp's backend is written in Erlang, it is not a fully Erlang-based application. The use of other technologies such as C and Java further reinforces the app's robust and efficient backend infrastructure.

The combination of Erlang's scalability and fault-tolerance, along with the performance and customization capabilities offered by C and Java, has enabled WhatsApp to deliver a messaging service that is both reliable and user-friendly to its vast global user base.

The future of WhatsApp's backend is likely to see ongoing improvements and optimizations, as the company continues to innovate and evolve its technology stack to meet the growing demands of its users.