Datomic vs MySQL vs PostgreSQL

Hello everyone,

Well, I want to build a large-scale project, but I do not know which ORDBMS to choose. The app should handle real-time operations, not chatting, but things like future scheduling or reminders. It should be also really secure, fast and easy to use. And last but not least, should I use them both. I mean PostgreSQL with Python / Django and MongoDB with Node.js? Or would it be better to use PostgreSQL with Node.js?

*The project is going to use React for the front-end and GraphQL is going to be used for the API.

Thank you all. Any answer or advice would be really helpful!

My data was inherently hierarchical, but there was not enough content in each level of the hierarchy to justify a relational DB (SQL) with a one-to-many approach. It was also far easier to share data between the frontend (Angular), backend (Node.js) and DB (MongoDB) as they all pass around JSON natively. This allowed me to skip the translation layer from relational to hierarchical. You do need to think about correct indexes in MongoDB, and make sure the objects have finite size. For instance, an object in your DB shouldn't have a property which is an array that grows over time, without limit. In addition, I did use MySQL for other types of data, such as a catalog of products which (a) has a lot of data, (b) flat and not hierarchical, (c) needed very fast queries.

Hi everybody, I'm developing an application to be used in a gym setting where athletes fill out a health survey, and coaches can analyze the results. However, due to the dynamic nature of some aspects of the app and more static aspects of the other, I am wondering if/how I would integrate MongoDB with my existing PostgreSQL database. I would like to store things like registrations, license information, and club information in Postgres, while I am thinking about moving things like user surveys, logging, and user settings information over to MongoDB. Some fields on the survey are integers, some large blocks of text, and some are arrays. My thought is, if I moved that data to MongoDB, it would give us greater flexibility in terms of adding and removing fields and data to them, and it would scale a lot easier than Postgres. Not to mention it will be easier to organize that kind of data. Is that overkill or am I approaching this issue the right way? Thank you!