S3 is just files and Lambda is just FaaS, you can host your own open source versions of these tools and not encounter an issue. This would be a more solid argu

S3 is just files and Lambda is just FaaS, you can host your own open source versions of these tools and not encounter an issue. This would be a more solid argument if they were using a lot of AWS features together, but you could replace this with Minio and FastCGI if you really wanted to.