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scale_web_app.md

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Web app scale from monolithic to distributed

1. Single Server + Database

01-initial-700.png

MVC Design:

  • Advantage:

    • Easy to debug
    • Easy to deploy

  • Disadvantage:

    • very difficult to scale. Each request is handled by the server and one page can have many requests which will consume lots of server resources
    • whenever there is a server issue, entire site goes down
    • deployment goes with both front end or backend end

2. Adding a Reverse Proxy

02-reverse-proxy-700.png

  • Health Checks make sure that our actual server is still up and running
  • Routing forwards a request to the right endpoint
  • Authentication makes sure that a user is actually permitted to access the server
  • Firewalling ensure that users only have access to the parts of our network they are allowed to use ... and more

3. Add a Load Balancer with multiple servers

03-load-balancer-700.png

  • Reverse Proxy can act as load balancer

4. Add more database to each server

04-database-scale-700.png

How to ensure data consistency:

  • Master/Slave setup or Write with Read-replicas: split into multiple parts where each part does its own thing

5. Microservices

05-microservices-700.png

  • each service can be scaled individually, enabling us to better adjust to demand
  • development teams can work independently, each being responsible for their own microservice's lifecycle (creation, deployment, updating etc.)
  • each microservice can use its own resources

6. Caching & CDN(Content Delivery Networks)

06-cdn-700.png

  • cache the static content

7. Message Queues

07-message-queue-700.png

Advantages:

  • it decouples tasks and processors. Sometimes a lot of images need to be processed, sometimes only a few. Sometimes a lot of processors are available, sometimes its just a couple. By simply adding tasks to a backlog rather than processing them directly we ensure that our system stays responsive and no tasks get lost.
  • it allows us to scale on demand. Starting up more processors takes time - so by the time a lot of users tries to upload images, it's already too late. By adding our tasks to a queue we can defer the need to provision additional capacities to process them

8. Sharding

08-sharding-700.png

  • Sharding can be based on any number of factors, e.g. letters, location, usage frequency (power-users are routed to the good hardware) and so on.
  • You can shard servers, databases or almost any aspect of your stack this way, depending on your needs.

9. Load-balancing the load-balancer

09-dns-700.png

  • DNS (Domain Name System): allows us to specify multiple IPs per domain name, each leading to a different load balancer.

Reference:

More resources