Tiers

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What is a tier?

both logical and physical separation of components

Single-tier App

All components are located in the same machine. e.g. Maya, Photoshop…

Pros

  • no network latency
  • privacy data safe since no need to upload users’ data

Cons

  • efficiency bounds on the machine where the app lives on
  • app publisher has no control over the app (users decide whether update the app or not)
  • be vulnerable to being tweaked and reversed engineered

Two-tier App

client-server architecture

Three-tier App

client-backend-database. e.g. blog

N-tier App

What are these components?

  • cache
  • load balancer
  • database
  • queue (for asynchronous behavior)
  • search engine
  • customized business logic services

It is an implementation of the single-responsibility principle

decoupled. it’s easier to maintain. so, for example, we should not store business logic in the database. Also, it is easier to be scaled.

Layer & Tier

layers represent the conceptual/logical organization of the code (code level)

tiers represent the physical separation of components.