I had a discussion with my colleagues about my bachelor thesis.

Together we created within the last 18 month a REST-API where we use LDAP/LMDB as database (tree structured storage). Of course our data is relational and of course we have a high redundancy there. It's a 170 call API and I highly doubt that it's actually conforming REST.
Ensuring DB integrity is done in the backend and coding style there is "If we change it at one place, let's make sure to also change it everywhere else", so you get a good impression how much of spaghetti code we have there.

Now I proposed to code a solution in my bachelor thesis where we use a relational database (we even have an administrated Oracle DB with high availability) and have a write-only layer to also store the data in LDAP but my colleagues said that "it would add too much complexity to the system".
Instead I should write the relational layer myself and fetch the data somehow from the existing LDAP tree.

What the actual fuck, spaghetti code is what makes the system really unnecessarily complex so that no one will understand that code in 2 years.

Congratulations, you just created legacy code that went into production in 2018 while not accepting the opportunity to let that legacy code get eliminated.
Now good luck with running and maintaining that system and it's inconsistencies.