If your use case fits S3 (eventually consistent updates are okay, no complex query model), you should almost always prefer it to RDS. S3 is usually cheaper than

If your use case fits S3 (eventually consistent updates are okay, no complex query model), you should almost always prefer it to RDS. S3 is usually cheaper than RDS (lots of updates may negate this, but storage costs and then usage based billing = most cases are cheaper. If your DB load is so low that you can reuse it between projects, and your query model is sufficiently simple that S3 could serve it up, you might try running some numbers). It also scales transparently, and infinitely. RDS requires downtime to scale horizontally, and goes only so far. The general suggestion, from AWS themselves, is to try and fit things into S3 first, and only go for RDS (or DynamoDB) if it makes sense to. Barring a clear indicator, S3 will almost always be cheaper, and has no scaling concerns. That's also been our experience; defaulting to S3 has been the cheapest, and required the least maintenance from us, and only when we come up with a good reason (need for complex or high performance queries, generally) did it ever make sense for us to reach for RDS or DynamoDB.