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How to Migrate a web app using Azure API Management

Updated: Nov 28, 2023

Azure API Management is a hybrid, multicloud management platform for APIs across all environments. This article provides an overview of common scenarios and key components of API Management.


APIs enable digital experiences, simplify application integration, underpin new digital products, and make data and services reusable and universally accessible. With the proliferation and increasing dependency on APIs, organizations need to manage them as first-class assets throughout their lifecycle.

Azure API Management helps customers meet these challenges

  • Abstract backend architecture diversity and complexity from API consumers

  • Securely expose services hosted on and outside of Azure as APIs

  • Protect, accelerate, and observe APIs

  • Enable API discovery and consumption by internal and external users

Common scenarios include

Unlocking legacy assets

APIs are used to abstract and modernize legacy backends and make them accessible from new cloud services and modern applications. APIs allow innovation without the risk, cost, and delays of migration.

API-centric app integration

APIs are easily consumable, standards-based, and self-describing mechanisms for exposing and accessing data, applications, and processes. They simplify and reduce the cost of app integration.

Multi-channel user experiences

APIs are frequently used to enable user experiences such as web, mobile, wearable, or Internet of Things applications. Reuse APIs to accelerate development and ROI.

B2B integration

APIs exposed to partners and customers lower the barrier to integrate business processes and exchange data between business entities. APIs eliminate the overhead inherent in point-to-point integration. Especially with self-service discovery and onboarding enabled, APIs are the primary tools for scaling B2B integration.

Solution Background

An e-commerce company in the travel industry is modernizing their legacy browser-based software stack. While their existing stack is mostly monolithic, some SOAP-based HTTP services exist from a recent project. They are considering the creation of additional revenue streams to monetize some of the internal intellectual property that's been developed.

Goals for the project include addressing technical debt, improving ongoing maintenance, and accelerating feature development with fewer regression bugs. The project will use an iterative process to avoid risk, with some steps performed in parallel:

  • The development team will modernize the application back end, which is composed of relational databases hosted on VMs.

  • The in-house development team will write new business functionality that will be exposed over new HTTP APIs.

  • A contract development team will build a new browser-based UI, which will be hosted in Azure.

New application features will be delivered in stages. These features will gradually replace the existing browser-based client-server UI functionality (hosted on-premises) that powers their e-commerce business today.

The management team does not want to modernize unnecessarily. They also want to maintain control of scope and costs. To do this, they have decided to preserve their existing SOAP HTTP services. They also intend to minimize changes to the existing UI. Azure API Management (APIM) can be used to address many of the project's requirements and constraints.


Azure API Management

The new UI will be hosted as a platform as a service (PaaS) application on Azure, and will depend on both existing and new HTTP APIs. These APIs will ship with a better-designed set of interfaces enabling better performance, easier integration, and future extensibility.



  • If the organization was planning to move their infrastructure entirely to Azure, including the VMs hosting the legacy applications, then APIM would still be a great option since it can act as a facade for any addressable HTTP endpoint.

  • If the customer had decided to keep the existing endpoints private and not expose them publicly, their API Management instance could be linked to an Azure Virtual Network (VNet):

o In an Azure "lift and shift" scenario linked to their deployed Azure virtual network, the customer could directly address the back-end service through private IP addresses.

o In the on-premises scenario, the API Management instance could reach back to the internal service privately via an Azure VPN gateway and site-to-site IPSec VPN connection or ExpressRoute making this a hybrid Azure and on-premises scenario.

  • The API Management instance can be kept private by deploying the API Management instance in Internal mode. The deployment could then be used with an Azure Application Gateway to enable public access for some APIs while others remain internal.


Availability and scalability


API Management is offered in four tiers: developer, basic, standard, and premium. You can find detailed guidance on the difference in these tiers at the Azure API Management pricing guidance here.

Customers can scale API Management by adding and removing units. Each unit has a capacity that depends on its tier.

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