All Things Scalability

All Things Scalability

Scale out vs Scale Up


Scalability is an application's ability to handle an increased load without a decrease in performance or availability.

Types of Scaling

Vertical Scaling (Scaling Up)

  • Here, we add more resources to handle the high traffic being experienced.

  • This is the easiest way to scale up your application. Since the application's logic doesn't care about machine resources, nothing special is needed to perform scaling up.

  • Scaling up is not enough due to the following:

    • Machine resources i.e. Memory, CPU, and storage are limited. Hence, you can't scale up endlessly.

    • Powerful machines are expensive.

    • In case your application is deployed to a single machine, if/when this machine goes down, your application becomes unavailable.

    • It's hard to deploy an application to a single machine without any downtime.

    • Machine maintenance is impossible without application downtime.

Horizontal Scaling (Scaling Out)

Client-side Traffic Balancing

  • Domain Name System: You can use multiple IP Addresses for a single domain name and balance traffic between these IPs using different algorithms (round-robin is the most popular).
  • Client-side: The client needs to know the server addresses and balance traffic between them by itself. This usually involves a library developed by server application owners that clients can use. Clients won't implement traffic balancing on their own.

Server-side Traffic Balancing

  • Load Balancer: Server that distributes incoming traffic across multiple servers. There are both hardware and software load balancers. Examples of Popular Software Load Balancer are:

    1. NGINX: Web server and reverse proxy that can be used as a load balancer

    2. HAProxy: Free, Open-source, reliable, high-performance TCP/HTTP load balancer.

    3. Apache HTTP Server: Web Server that can be used as a load balancer.