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Isolating the Three Tiers

  • Article
  • 11/12/2009

Most Internet services require configurations that separate the user interface tier from the business logic tier and the database tier to simplify administration.

The following figure shows how many e-commerce sites further isolate business logic from underlying data.

A figure that illustrates multi-tiered e-commerce site architecture

In a multi-tiered configuration, such as the one shown here, client browsers access Web pages and the Web pages activate associated business logic hosted on a Web server. The persistent data that the business objects require is maintained in a separate database tier.

Data and state information control processing logic and client experience. The following table describes typical design strategies you can use for isolating each tier.

Tier Strategy
User interface tier
  • Low state (does not hold much application code state information), unique data stored in cookies or registry.
  • Wide variety of low-end servers.
  • Minimize downtime by using additional servers.
Business logic tier
  • Web applications, such as the Product Catalog System, Profiling System, and Business Process Pipelines, run on this tier.
  • Low state, no unique data, inexpensive servers.
  • Minimize downtime by using software or hardware single-Internet Protocol (IP) load balancing.
Database tier
  • Data that Commerce Server uses is managed and stored in the Data Warehouse on this tier.
  • System state and data are stored on this tier.
  • Minimize downtime by using a clustered or replicated configuration.

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