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As i know yugabyte store data in something called DocDB and it provide YSQL API and YCQL API over that.

So if i'm not wrong, Are YSQL and YCQL compatible with each other?

For example: Can i create a table with YSQL and query on it with YCQL?

And if NOT, Could be any performance-diffrence between YSQL and YCQL? I mean, should we care about choosing YSQL or YCQL in a project?

Ali Zeinali
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Thanks for the question - what Jose mentioned is correct (as of now):

The YugabyteDB APIs are isolated and independent from one another today. This means that the data inserted or managed by one API cannot be queried by the other API. Additionally, there is no common way to access the data across the APIs (external frameworks such as Presto can help for simple cases).

Over time, we should be able to allow the YCQL tables to be "accessed" from YSQL (which is fully PostgreSQL compatible) as a foreign table using foreign data wrappers (FDW). Note that the work for this has not yet started, but it is fully possible to do in the current architecture.

Performance Differences

Yes, there are differences in the performance as Jose pointed out, but this is the current state of things as well. YCQL is higher performing at the moment that YSQL due to various reasons, and we are rapidly closing the gap. This is something we intend to write about a lot more over time.

In the short term, I would recommend the following:

  • If you need relational features (say foreign keys) or query flexibility (say joins) in your app, YSQL is the way to go. Again, we expect to get it close to YCQL over the next 3-6 months for most use-cases.
  • If you do not need the above but are talking about a lot of data (say over 10TB of data), care about very low latencies (sub-millisecond) and have a need for features such as automatic data expiry using the TTL feature - you should use YCQL.

If you have a use case in mind, we are happy to help you decide with a more detailed analysis. Please also consider joining the community slack channel for realtime support.

Karthik Ranganathan
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The YugabyteDB APIs are isolated and independent from one another today. This means that the data inserted or managed by one API cannot be queried by the other API. Additionally, there is no common way to access the data across the APIs (external frameworks such as Presto can help for simple cases).

The net impact is that application developers have to select an API first before undertaking detailed database schema/query design and implementation. See the docs

I'm not a Yugabyte expert, but according to docs: Yes there are performance differences between YSQL and YCQL. See slide 18 at enter link description here

Jose Flores
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