WSO2 ESB - Serving Multiple Modern Apps from a Slow Legacy System

The story of serving thousands of requests sent by multiple modern applications in the downstream from a system that serves only 2 requests per second, basically how to get more bang from the existing buck!


Scenario - Vehicle Licensing Department of the Liliput Kingdom is going through digital transformation. As a step in this process they are going to introduce multiple applications to their manual processes. The apps can include,

• Mobile app running on vehicle owner's devices to check their vehicle licenses
• Customer service web app to check status of vehicle licences
• EverGreen - a third party organization that check vehicle emissions. It needs to get details of the licenses and vehicles.
• The vehicle license printing service needs to be automated

All the vehicle license information in a mainframe(MF) and this MF has one method for listing all the vehicle licenses. Calls for this method cannot exceed 2 per second. The goals of the architecture,

• Implement a solution by retrieving records from MF
• Expose REST services for the mobile, webapps and third parties
• Expose a SOAP API that the printing service is capable of calling
• Calls to down stream must not exceed 2 calls per second
• Calls to MF should be done over CICS

This is the solution proposed for Liliput VLD is based on WSO2 ESB. It helped VLD to remove point to point connections and perform mediation, transformation in minimal time.

High lights of the architecture,

• Create an intermediate database between the MF and new system - let's call it IDB
• Periodically retrieve delta from the MF and update the IDB
• Expose the data in IDB as a REST service
• Integrate data using the ESB to create composite interfaces
• Expose all APIs over APIM to be consumed by applications. This provides throttling, security and API analytics

The Vehicle Licensing Department of Liliput Kingdom achieved digital transformation much faster and less cost, due to this architecture.