I've been working on serverless applications for years now and the cases are quite rare TBH.
Static cost of data streams come up in data projects but even there it's trivial to consume data from shared streams in developer-specific environment since the stream pointer is managed in client side. The throughput required by even multiple occasionally consuming dev environments rarely requires provisioning streams above minimum capacity.
DynamoDB in on-demand mode is my go-to OLTP database until I know enough of runtime load characteristics to provision static capacity with autoscaling. For any non-prod (or load testing) environment on-demand mode is the best choice. Aurora Serverless is OK as well but has its warts and so far the cases where I really need a relational database in a greenfield project have been few and far between. Anything with complex query requirements goes to S3 and gets queried asynchronously or in batches via Athena. Not suitable for real-time cases though.
Things like queues, notifications and e-mails are handled by SQS or SNS and paid per usage. Websockets by API Gateway and Lambda.
Architecting for serverless requires a shift in mindset and tooling but as a benefit you get cheap isolated development environments and truly elastic production environments with very little ops burden.
Static cost of data streams come up in data projects but even there it's trivial to consume data from shared streams in developer-specific environment since the stream pointer is managed in client side. The throughput required by even multiple occasionally consuming dev environments rarely requires provisioning streams above minimum capacity.
DynamoDB in on-demand mode is my go-to OLTP database until I know enough of runtime load characteristics to provision static capacity with autoscaling. For any non-prod (or load testing) environment on-demand mode is the best choice. Aurora Serverless is OK as well but has its warts and so far the cases where I really need a relational database in a greenfield project have been few and far between. Anything with complex query requirements goes to S3 and gets queried asynchronously or in batches via Athena. Not suitable for real-time cases though.
Things like queues, notifications and e-mails are handled by SQS or SNS and paid per usage. Websockets by API Gateway and Lambda.
Architecting for serverless requires a shift in mindset and tooling but as a benefit you get cheap isolated development environments and truly elastic production environments with very little ops burden.