Based on personal experience, I found that paying for the setup, tuning and 24/7 maintenance of a dedicated is way more expensive than using those service.

But I'm one of those crazy people who considers their time and that worth something.

Excuse the snark, but these arguments just keep repeating themselves. There's a reason they're called "services". It's like saying "it's cheaper to slaughter your own cow than to eat at a restaurant".

This is true only if your time is free or you're cutting corners on reliability. For example, using an EC2 medium instance on-demand is $0.120/hour and RDS is $0.160/hour. If you use enough MySQL, that $0.04/hour (in reality, $0.022 at reserved rates) can reach the point where it's worth rolling your own management stack, backups, failover, etc. but there are many people who will never reach the point where they don't have higher-priority investments to make.

+1 for Mongodb on a EC2 instance instead of Dynamodb

We're transitioning off Dynamo as soon as possible as the billing structure makes it either a real headache or very expensive.

For example: if you want to make a backup of a large table or move data around, it'll either take days or cost you an arm and a leg. This is just one of many annoyances. Ever since making the decision to go with Dynamo over Mongo, I've been getting dirty looks from my team.

The set of problems where you're really struggling between mongodb and dynamodb as a choice is practically non-existent. They have hugely different characteristics and vastly different trade-offs. You might want to spend some time reading about the architecture of various databases before just picking one.

Two things:

1. What kind of EC2 instance are we talking about for MongoDB? If you're not using an SSD, comparing Dynamo and Mongo wouldn't be an apples-to-apples comparison.

2. I buy that the strictly technical costs of these systems is lower, but I'm not certain I buy that the overall cost (including engineer time to set these services up and monitor them) is lower.

1. With a provisioned iops the performance is almost identical to SSD, but yes probably I haven't done a side-to-side technical comparison. I only wanted to point out that I replaced one with the other and I had a good cut in cost.

2. Maybe it is just me, but I really think that some services like mongodb/redis does not require a big amount of system administration work to setup, I have actually wrote many python scripts to automate most of these tasks. but again maybe this depends on the country and the IT culture.

I see what you're getting at, but I'd like to point out that "not a big amount of system administration work" isn't worth money. Have you actually figured out how much it costs you to write many python scripts?

If you have the staff, I definitely can see this. For a small team (in my case, 2) RDS was a no brainer. More than anything, letting Amazon handle backups was a big win. However, in a use case where you need more control (I realize you can ssh/rdp in, but there are limited configuration options) or more performance (the highest performing instance types aren't available) or flexibility (for SQL Server, you can't perform the full range of import, etc activities due to permissions), RDS may not be the best fit.

I think you wanted to say "on an EC2 machine", instead of "dedicated machine". Otherwise, people might think you're referring to physical hardware.

At scale this is probably cheaper, if your a startup trying to scale, probably not.

It depend on the service. Usually scale is not a problem, but scale in a short time (hours) can be a huge problem. But most companies would love to have this problem ;-)

why even use EC2 then? It would be much cheaper to use any other hosting provider.