Scalable application architecture refers to designing and developing applications in such a way that they can easily handle increasing user loads and data volume over time. Node.js is particularly suited for developing scalable applications due to its event-driven, non-blocking I/O model that enables it to handle a large number of concurrent connections efficiently.

To build a scalable application architecture in Node.js, developers need to apply several best practices, both on the server-side and client-side.

1. Use a load balancer: A load balancer distributes incoming requests across multiple server instances, thus preventing one server from becoming overloaded. Node.js can be easily integrated with popular load balancers like Nginx or HAProxy.

2. Cluster the servers: Node.js includes a built-in cluster module that allows multiple Node.js processes to work together as a single server. Clustering Node.js servers can help balance workloads and provide failover redundancy when one server goes down.

3. Use scalable data storage: Node.js can work with NoSQL databases like MongoDB which have a horizontal scaling architecture, providing flexible and efficient data storage.

1. CDN (Content Delivery Network): a CDN distributes the load of the static content (images, videos, etc.) to different servers geographically located worldwide.

2. Caching: by caching the data on the client-side and server-side, we can minimize data traffic, reduce network latency, and provide faster loading times to users.

3. Scalable front-end architecture: using technologies like ReactJS or VueJS, developers can build front-end components that can be reused and scaled as the application grows.

By implementing these best practices, developers can build Node.js applications that will continue to deliver the required performance, even as the user load and data volume grow.