MongoDB

MongoDB is a popular document-oriented NoSQL database that stores data in flexible documents rather than the rows and columns of classic tables. Each document is a BSON structure (a binary flavour of JSON), which lets you store nested data with a variable schema within a single collection.

How MongoDB works

Instead of splitting a record across many related tables, MongoDB groups related data into a single document that can be retrieved whole, without costly joins. The key concepts that set it apart from relational databases:

• Document — a single record in BSON format with key–value pairs, including nested ones.
• Collection — a set of documents, the equivalent of a table but without an enforced schema.
• Replica set — a group of servers holding copies of the data for high availability and automatic failover.
• Sharding — horizontal partitioning of data across many servers, enabling scale beyond a single machine's capacity.

MongoDB in practice

MongoDB is a common choice for projects with dynamic or loosely structured data:

1. Product catalogues — different categories carry different attributes that a flexible document holds without schema changes.
2. Real-time applications — logs, events and telemetry written at high frequency.
3. Big Data systems — sharding spreads huge data volumes across many nodes.
4. Prototypes and rapid iteration — the schema-less model speeds up early development.

Running MongoDB calls for a server with enough RAM and fast disks — the database leans heavily on its cache, so a capable VPS or dedicated server has a direct impact on query response times.