Serverless Functions in Swift: AWS Lambda from A to Z

Introduction to Serverless on Swift with AWS Lambda

Serverless architecture is becoming the standard for modern cloud development. Thanks to AWS Lambda, developers can run code without managing servers, paying only for actual execution time. Until recently, Swift remained on the sidelines of the serverless world, but with the official support for Swift on AWS Lambda, the situation has changed dramatically.

In this article, we will cover the full lifecycle of working with serverless functions in Swift: from environment setup to production deployment. You will learn how to leverage your iOS/macOS development experience to create efficient cloud solutions.

Why Swift for Serverless?

Swift is not just a language for mobile applications. Its strengths make it an excellent choice for serverless:

• Type safety — the compiler catches errors at build time
• High performance — native code runs faster than interpreted languages
• Modern syntax — code is easy to read and maintain
• Shared codebase — you can reuse models and logic from iOS/macOS projects

To run Swift on AWS Lambda, the official Amazon Linux 2 image with pre-installed Swift 5.10 is used. This guarantees full compatibility and minimal cold start time.

Environment Setup and Creating Your First Function

Installing Required Tools

Before you begin, make sure you have installed:

• Swift 5.10 or newer
• Docker (for building in a Linux environment)
• AWS CLI with configured credentials
• Homebrew (for macOS)

# Install Swift via Homebrewbrew install swift

# Check versionswift --version

# Install AWS CLIbrew install awscli

# Configure AWSaws configure

Creating a Swift Package Project

Let's create a new executable Swift package:

mkdir MyLambdaFunctioncd MyLambdaFunctionswift package init --type executable

Now update Package.swift to work with the AWS Lambda Runtime:

// swift-tools-version:5.10import PackageDescription

let package = Package(    name: "MyLambdaFunction",    platforms: [.macOS(.v13)],    dependencies: [        .package(url: "https://github.com/swift-server/swift-aws-lambda-runtime.git", from: "1.0.0")    ],    targets: [        .executableTarget(            name: "MyLambdaFunction",            dependencies: [                .product(name: "AWSLambdaRuntime", package: "swift-aws-lambda-runtime")            ]),        .testTarget(            name: "MyLambdaFunctionTests",            dependencies: ["MyLambdaFunction"]),    ])

Handler Function Code

Replace the contents of Sources/MyLambdaFunction/main.swift:

import AWSLambdaRuntime

// Define the request structurestruct Request: Codable {    let name: String    let age: Int}

// Define the response structurestruct Response: Codable {    let message: String    let isAdult: Bool}

// Main handler@mainstruct MyHandler: SimpleLambdaHandler {    typealias Event = Request    typealias Output = Response

    func handle(_ event: Request, context: LambdaContext) async throws -> Response {        let isAdult = event.age >= 18        return Response(            message: "Hello, \\(event.name)!",            isAdult: isAdult        )    }}

Building and Deploying to AWS Lambda

Building for Linux

Since Swift on macOS builds binaries for macOS, we need to use Docker:

# Create a Dockerfilecat << EOF > DockerfileFROM swift:5.10-amazonlinux2 AS buildWORKDIR /appCOPY . .RUN swift build -c release --