Cowboy vs Passenger vs Puma: What are the differences?

# Introduction

Key differences between Cowboy and Passenger and Puma are outlined below:

1. **Concurrency Handling**:
Cowboy uses a single-threaded asynchronous model, while Puma and Passenger are multi-threaded. Cowboy relies on the Erlang VM for concurrency while Puma utilizes multiple threads within a process to handle incoming requests efficiently. Passenger, on the other hand, can spawn multiple processes to handle requests simultaneously.

2. **Configuration Flexibility**:
Passenger provides a user-friendly configuration interface with multiple options for customization, making it easy for developers to adjust settings according to their needs. Puma offers a more streamlined configuration process, ideal for developers looking for simplicity without sacrificing performance. Cowboy, being a low-level framework, requires more manual configuration and customization, suitable for advanced users.

3. **Community Support**:
Passenger has a large community of active users and contributors, resulting in frequent updates, bug fixes, and support. Puma also has a supportive community, but with a focus on performance tuning and optimizations. Cowboy, although reliable, has a smaller community compared to the other two frameworks, which may impact the availability of resources and assistance.

4. **Scalability**:
Puma is known for its superior scalability due to its multi-process/multi-threaded architecture, making it a popular choice for high-traffic applications. Passenger, with its process-spawning capabilities, offers good scalability as well. Cowboy, while highly performant and efficient, may not scale as easily in certain scenarios due to its design limitations.

5. **Integration with Web Servers**:
Passenger integrates directly with popular web servers like Apache and Nginx, offering seamless deployment options for developers. Puma, although capable of running as a standalone HTTP server, can also be integrated with web servers for added flexibility. Cowboy, being a standalone HTTP server, may require additional setup and configuration to work alongside web servers.

6. **Memory Footprint**:
Puma and Passenger tend to have a higher memory footprint compared to Cowboy, which can impact resource usage in memory-constrained environments. Cowboy, optimized for low memory consumption, may be preferable for applications where memory efficiency is a critical factor.

In Summary, Cowboy, Passenger, and Puma differ in concurrency handling, configuration flexibility, community support, scalability, integration with web servers, and memory footprint, offering developers a range of options based on their specific needs.