What is the candidate's level of proficiency in MongoDB?

The candidate's proficiency level in MongoDB can be assessed based on the following criteria:

• Junior: knows basic operations — creating, reading, updating, deleting documents (CRUD), can work with simple queries and indexes.
• Middle: understands BSON structure, can design data schemas, use aggregate functions, optimize queries, work with replication and sharding, knows basic administration and monitoring tools.

Example of a simple MongoDB query to find users older than 25:

db.users.find({ age: { $gt: 25 } })