How PayPal Was Able to Support a Billion Transactions per Day With Only 8 Virtual Machines

The post discusses how PayPal scaled to a billion daily transactions using only 8 virtual machines. Initially a security software team, PayPal pivoted to online payments due to a failed business model. As they grew, simply buying newer hardware did not solve scalability issues due to limitations in Moore's Law. They transitioned to the actor model based on the Akka framework for extreme scalability. In this model, lightweight actors process messages asynchronously via immutable data structures, enhancing concurrency and fault tolerance. While effective, the actor model introduces a learning curve and requires caution to prevent issues like race conditions. PayPal's success showcases the model's resource efficiency, making them handle high transaction volume effectively.