Scalability is not something that can be added later as an afterthought; it is a property that emerges from the application of sound design principles throughout your system. To achieve scalability, you should consider modularity, abstraction, reusability, decoupling, separation of concerns, and statelessness. Modularity involves breaking down your system into smaller, independent, and loosely coupled components that can be deployed, scaled, and updated separately. Abstraction requires hiding implementation details and complexity behind well-defined interfaces and contracts. Reusability helps to avoid duplication by reusing existing components or services with proven scalability and reliability. Decoupling reduces dependencies and interactions between components through asynchronous communication, message queues, event-driven architectures, and publish-subscribe patterns. Separation of concerns divides your system into different layers or tiers with distinct responsibilities and functions. Finally, statelessness minimizes the state information stored or maintained by components by using external services or databases to store and manage state data.