Minimal API with native AOT

Ok, now we've got the basics out of the way. Let's take a look at how to supercharge your cold start performance using .NET 7 native AOT.

Big disclaimer here! Microsoft DO NOT officially support ASP.NET for native AOT in .NET 7 (maybe in .NET 8). This approach is functional, but your mileage may vary

Start a new project

To demonstrate how to use native AOT with ASP.NET minimal API's on AWS Lambda let's continue right from where we left off in the last section. Adding native AOT support is pretty straightforward.

Package Versions

The first thing you'll need to do is ensure you're using version 1.5.0 or later of the Amazon.Lambda.AspNetCoreServer.Hosting package.

minimal-native-aot

<Project Sdk="Microsoft.NET.Sdk.Web">

<PropertyGroup>

<TargetFramework>net7.0</TargetFramework>

<Nullable>enable</Nullable>

<ImplicitUsings>enable</ImplicitUsings>

</PropertyGroup>

<ItemGroup>

<PackageReference Include="Amazon.Lambda.AspNetCoreServer.Hosting" Version="1.5.0" />

</ItemGroup>

</Project>

Source Generated Serialization

The second thing you'll need to do is add a new partial class to your project. This class will configure a source generated serializer. Source generated serializers generate classes at compile time to work with JSON, as opposed to the reflection based approach used in System.Text.Json and Newtonsoft.Json.

minimal-native-aot

using System.Text.Json;

using Amazon.Lambda.APIGatewayEvents;

namespace MinimalApi.OnLambda;

[JsonSerializable(typeof(WeatherForecast))]

[JsonSerializable(typeof(APIGatewayHttpApiV2ProxyRequest))]

[JsonSerializable(typeof(APIGatewayHttpApiV2ProxyResponse))]

public partial class ApiSerializationContext : JsonSerializerContext

{

}

Using Statements

Add two additional using statements. One for the Amazon Lambda serialization libraries, and one to ensure the ApiSerializationContext is available to the Program.cs file.

minimal-native-aot

using Amazon.Lambda.Serialization.SystemTextJson;

using MinimalApi.OnLambda;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddAWSLambdaHosting(LambdaEventSource.HttpApi, options =>

{

options.Serializer = new SourceGeneratorLambdaJsonSerializer<ApiSerializationContext>();

});

builder.Services.ConfigureHttpJsonOptions(options =>

{

options.SerializerOptions.AddContext<ApiSerializationContext>();

});

var app = builder.Build();

// Configure the HTTP request pipeline.

var summaries = new[]

{

"Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"

};

app.MapGet("/weatherforecast", () =>

{

var forecast = Enumerable.Range(1, 5).Select(index =>

new WeatherForecast

(

DateOnly.FromDateTime(DateTime.Now.AddDays(index)),

Random.Shared.Next(-20, 55),

summaries[Random.Shared.Next(summaries.Length)]

))

.ToArray();

return forecast;

});

app.Run();

public record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)

{

public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);

}

AWS Lambda Hosting Configuration

Second, you'll need to add an additional parameter to the AddAWSLambdaHosting method. With this parameter you can configure the serializer for the AWS tooling to use. This allows the inbound payload from API Gateway to be (de)serialized into a request ASP.NET understands. The SourceGeneratorLambdaJsonSerializer class is provided by the Amazon.Lambda.Serialization package.

minimal-native-aot

using Amazon.Lambda.Serialization.SystemTextJson;

using MinimalApi.OnLambda;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddAWSLambdaHosting(LambdaEventSource.HttpApi, options =>

{

options.Serializer = new SourceGeneratorLambdaJsonSerializer<ApiSerializationContext>();

});

builder.Services.ConfigureHttpJsonOptions(options =>

{

options.SerializerOptions.AddContext<ApiSerializationContext>();

});

var app = builder.Build();

// Configure the HTTP request pipeline.

var summaries = new[]

{

"Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"

};

app.MapGet("/weatherforecast", () =>

{

var forecast = Enumerable.Range(1, 5).Select(index =>

new WeatherForecast

(

DateOnly.FromDateTime(DateTime.Now.AddDays(index)),

Random.Shared.Next(-20, 55),

summaries[Random.Shared.Next(summaries.Length)]

))

.ToArray();

return forecast;

});

app.Run();

public record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)

{

public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);

}

Pass Serialization Context to ASP.NET

The serialization context is also passed into ASP.NET's HTTP JSON options. This let's the ASP.NET model binding use the source generated serializers generated at compile time.

minimal-native-aot

using Amazon.Lambda.Serialization.SystemTextJson;

using MinimalApi.OnLambda;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddAWSLambdaHosting(LambdaEventSource.HttpApi, options =>

{

options.Serializer = new SourceGeneratorLambdaJsonSerializer<ApiSerializationContext>();

});

builder.Services.ConfigureHttpJsonOptions(options =>

{

options.SerializerOptions.AddContext<ApiSerializationContext>();

});

var app = builder.Build();

// Configure the HTTP request pipeline.

var summaries = new[]

{

"Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"

};

app.MapGet("/weatherforecast", () =>

{

var forecast = Enumerable.Range(1, 5).Select(index =>

new WeatherForecast

(

DateOnly.FromDateTime(DateTime.Now.AddDays(index)),

Random.Shared.Next(-20, 55),

summaries[Random.Shared.Next(summaries.Length)]

))

.ToArray();

return forecast;

});

app.Run();

public record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)

{

public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);

}

Package Versions

The first thing you'll need to do is ensure you're using version 1.5.0 or later of the Amazon.Lambda.AspNetCoreServer.Hosting package.

Source Generated Serialization

The second thing you'll need to do is add a new partial class to your project. This class will configure a source generated serializer. Source generated serializers generate classes at compile time to work with JSON, as opposed to the reflection based approach used in System.Text.Json and Newtonsoft.Json.

Using Statements

Add two additional using statements. One for the Amazon Lambda serialization libraries, and one to ensure the ApiSerializationContext is available to the Program.cs file.

AWS Lambda Hosting Configuration

Second, you'll need to add an additional parameter to the AddAWSLambdaHosting method. With this parameter you can configure the serializer for the AWS tooling to use. This allows the inbound payload from API Gateway to be (de)serialized into a request ASP.NET understands. The SourceGeneratorLambdaJsonSerializer class is provided by the Amazon.Lambda.Serialization package.

Pass Serialization Context to ASP.NET

The serialization context is also passed into ASP.NET's HTTP JSON options. This let's the ASP.NET model binding use the source generated serializers generated at compile time.

minimal-native-aot

<Project Sdk="Microsoft.NET.Sdk.Web">

<PropertyGroup>

<TargetFramework>net7.0</TargetFramework>

<Nullable>enable</Nullable>

<ImplicitUsings>enable</ImplicitUsings>

</PropertyGroup>

<ItemGroup>

<PackageReference Include="Amazon.Lambda.AspNetCoreServer.Hosting" Version="1.5.0" />

</ItemGroup>

</Project>

And that's it! That is all you need to do to enable native AOT for your ASP.NET minimal API's, and run them on AWS Lambda.

If your video is more your thing, I have a walkthrough on my YouTube channel that covers these same concepts.