Business critical application development is heavily reliant on large telecom capacity. Smaller or low volume IVR applications are typically fine running on a single T1, which in turn requires a single IVR server. 

For businesses that need enterprise level IVRs, systems require multi-tier (either 3 or 4 tier) architecture to function at the requisite levels and integrate efficiently with databases. 

4-tier architecture describes client-server architecture that stratifies and separates application functionality in to separate processes. Application processing, data management, and presentation are executed as separate events in this type of architecture. 

In terms of web development, breaking up applications into tiers allows developers to amend only specific components when modification is required. 

Plum’s applications typically operate utilizing four-tier architecture, with the Plum VoiceXML platform, the Call Flow Application Server, the Business Logic Server, and the Customer Data existing on separate tiers. 

Developers looking to build this type of four-tier architecture for IVR systems should, first and foremost, be able to code VoiceXML (News - Alert) (in order to link the VXML Platform with the Call Flow App Server). From there, developers need to utilize SOAP and XML to synthesize the Call Flow App Server and the Business Logic Server. After project management has received the raw SQL data complete with business logic from the client, developers must also synchronize the Business Logic Server with client data. 

Typically, this type of multi-tier architecture requires a developer on the client side that is a database programmer. From the Plum side, multi-tier architecture construction requires someone with the following four skills: database programming, application server development, the ability to write web services, and VoiceXML programming experience. Any developer who has this well-rounded background will successfully be able to edit any layer or tier of multi-tier architecture effectively and efficiently.