Database engine choice for Django/ Python application
use postgreSQL, our team worked with sqlite3 for a long time. However, when you import data to db,it often give the information 'database is locked!'
The advantages of sqlite3

it is small,as you put it, no server setup needed
max_length in models.py is not strictly, you set max_length=10, if you put 100 chars in the field, sqlite3 never complain about it,and never truncate it.

but postgreSQL is faster than sqlite3, and if you use sqlite3.
some day you want to migrate to postgreSQL, It is a matter beacuse sqlite3 never truncate string but postgreSQL complains about it!
I am working on a Python/Django application. The core logic rests in a Python application, and the web UI is taken care of by Django. I am planning on using ZMQ for communication between the core and UI apps. 
I am using a time-series database, which uses PostgreSQL in the background to store string data, and another time-series tool to store time-series data. So I already have a PostgreSQL requirement as part of the time-series db. But I need another db to store data (other than time-series), and I started work using PostgreSQL. 
sqlite3 was a suggestion from one of my team members. I have not worked on either, and I understand there are pros and cons to each one of them, I would like to understand the primary differences between the two databases in question here, and the usage scenarios.