The ZODB is and was a Python pickle store in the first place. The question about what makes a "database" can be answered differently. Functionality like indexes

The ZODB is and was a Python pickle store in the first place. The question about what makes a "database" can be answered differently. Functionality like indexes and query languages are in the Zope world application level functionality build on top of the ZODB. The ZODB turned out being a database solution for many large scale projects (up to several 100 GB). There are options for sharding (mount points) and replications (ZRC, Relstorage). The ZODB is unlikely the solution that you would use nowadays for "big data" however keep in mind that the ZODB is already 15 years old and severed many people in professional solutions for more than a decade. We know of many businesses still using the ZODB in mission critical applications. But yes, the ZODB is an object store and not a RDBMS - it's a completely different beast - like always: use the right tool for each project. And the ZODB was already "NoSQL" by the end of the 90s of the last millennium. No need to hate the ZODB - it is just another database option - and in some case I would still use the ZODB today over tinkered garbage database solutions like MongoDB having a braindead replication and sharing model.