i've never deployed a SSR node app, however depending on the size / complexity of your API, i'd recommend using lambda and apigateway to serve the API/SSR, the static site in S3, S3 costs are very reasonable, sat behind cloudfront to serve cached content globally. using the serverless resources in AWS is always a good idea because they're cheap (depending on usage) and give you scaling OOTB, meaning you don't need to worry about infrastructure running & costs