Source code for blog:
ASP.NET Core Serverless Web API running in AWS Lambda, using API Gateway HTTP API, with a Lambda Warmer
Simply specifying DomainName, CertificateArn, and Route53 HostedZoneId in aws-lambda-tools-defaults.json, and then running dotnet lambda deploy-serverless will spin up the entire infrastructure (HTTP API for Amazon API Gateway) and an ASP.NET Core Web API (running inside a Lambda) in minutes, ready to serve requests in a serverless and scalable way.
Remember to also choose an existing s3-bucket for your assets in aws-lambda-tools-defaults.json.
Once deployed just hit the API endpoint https://api.mydomain.com/api/values to make sure it's all working. (change to use your own domain name)
If your DNS is hosted elsewhere (or in another AWS account), just remove the DNSRecordA resource in serverless.template, and update the CNAME manually.
If you don't want a domain name (might be the case for Hackathons), also remove the ApiGatewayDomainName and ApiGatewayBasePathMapping resources in serverless.template, and you can hit your API via the API Gateway generated URL, which will be outputted as ApiURL.
A Lambda Warmer is also included doing an effective job in forgoing cold starts by specifying the number of instances you want to keep warm.
A CodeBuild buildspec.yaml file is provided to deploy this out. I recommend choosing the aws/codebuild/amazonlinux2-x86_64-standard:3.0 environment image, as PublishReadyToRun is set to true to further improve the performance of the API.
If deploying locally from a Windows PC, set PublishReadyToRun to false in the .csproj file. You must have the .NET Core 3.1 SDK installed, as well as the Amazon.Lambda.Tools dotnet tool install -g Amazon.Lambda.Tools.