Introduction

The multi-tier application (three-tier, n-tier, etc.)

has been a cornerstone architecture pattern for decades.

The multi-tier pattern provides good guidelines for you to follow to ensure decoupled and scalable application components that can be separately managed and maintained (often by distinct teams).

Multitiered applications are often built using a service-oriented architecture (SOA) approach to using web services.

In this approach, the network acts as the boundary between tiers.

However, there are many undifferentiated aspects of creating a new web service tier as part of your application.

Much of the code written within a multi-tier web application is a direct result of the pattern itself.

Examples include code that integrates one tier to another, code that defines an API and a data model that the tiers use to understand each other, and securityrelated code that ensures that the tiers’ integration points are not exposed in an undesired way.

Amazon API Gateway1, a service for creating and managing APIs, and AWS Lambda2, a service for running arbitrary code functions, can be used together to simplify the creation of robust multi-tier applications.

Amazon API Gateway’s integration with AWS Lambda enables user defined code functions to be triggered directly via a user-defined HTTPS request.

Regardless of the request volume required, both the API Gateway and Lambda will scale automatically to support exactly the needs of your application.

When combined, you can create a tier for your application that allows you to write the code that matters to your application and not focus on various other undifferentiating aspects of implementing a multi-tiered architecture—like architecting for high availability, writing client SDKs, server/operating system (OS) management, scaling, and implementing a client authorization mechanism.

More recently, AWS has announced the ability to create Lambda functions that execute within your Amazon Virtual Private Cloud (Amazon VPC).

This feature extends the benefits of combining API Gateway and Lambda to include a variety of use cases where network privacy is required.

For example, when you need to integrate your web service with a relational database that contains sensitive information.

The integration of Lambda and Amazon VPC has indirectly expanded the capabilities of Amazon API Gateway because it gives developers the