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29 October 2019
SQL as a Service
I’ve been thinking about this since 2007, somewhere around the time S3 was launched by Amazon. I even tried to implement it a few times, but failed right after the design phase. I’ve heard about a startup, which tried to do it too, but also failed. I’m still not sure whether it’s possible to do, but it could definitely become a best seller in the market of cloud data management. Wait, you may say, what about Google Cloud SQL, AWS RDS, Microsoft Azure, Heroku PostgreSQL, and many others? They are not even close to what I mean.
Let me give you an analogy. Say you want to store a piece of binary data in the cloud. I have two solutions for you. The first one is a hosted server with FTP. You pay me $5 per month, I give you FTP access to the server, which has a disk of 100Gb. You can upload your files there and download back. Works just fine. And I have a second option, which is AWS S3. You can also upload and download your data, but via their API. And you pay for each API request, each byte hosted, and each byte transferred, instead of a monthly fee. Which one would you choose?
Obviously, you would go with S3. Why? What is the fundamental difference between these two? The key difference is in their SLAs: The first one with an FTP is a server, the second one is a service.
An FTP server provider guarantees you the availability of computational resources (CPU, disk, bandwidth, etc.), while S3 guarantees you the availability of the data. If the disk on the FTP server crashes it will be replaced in a timely manner, but the data will be lost. If the disk gets full, you will be able to order an additional server, but it’s your responsibility not to forget. If the disk space is not used, you still pay $5 per month. And so on.
AWS S3 was such a breakthrough in the market, more than ten years ago, precisely because of this difference. They added a new service layer on top of the good old web hosting we were all used to. The idea remained the same—it’s still data in the cloud, which we upload and download—but the SLA was different. We didn’t need to worry anymore about disk overflow, paying too much for unused space, regular backups, SSH terminals, and many more things. They just gave us a simple API and a promise that the data was there and was safe.
It’s 2019 now and we still don’t have the same for relational data. No matter which provider you choose, all they do is give you a machine (or a cluster) with MySQL or PostgreSQL installed (or their own version of them) and charge you per hour of uptime. They still give you the “good old FTP” without an additional service layer on top of it.
This is what I would expect a true relational-data-in-the-cloud SLA to sound like:
Auto-scale. Don’t make us worry about the amount of resources required to host the data. Just charge more for larger data sets and make sure our requests come back in a predictable amount of time.
Pay-per-data. Make us pay for each SQL request, each byte stored, and each byte transferred. How many servers and disks are required to host it all—that must not be of our concern.
Indexes. Create them automatically, using the statistics of the SQL queries we are making.
Schema Versioning. Make it possible to update the schema via something similar to Liquibase: we create a new
CREATE TABLEscript and it gets applied to the existing database.
Snapshots and Rollbacks. Make it possible to make a snapshot of the data, apply a new schema version, and then rollback to one of the previously made snapshots if something is wrong.
Is it really so hard to implement?