Types of Databases & When to Use them
Databases are knowledge gods of our application (Fun term right? Yeah I think so too). And just like gods Databases are many, we have so many options to choose from.
When you're a backend developer you cannot dodge this question in interviews. The understanding not just helps you in the interview but also signals that you're a developer who knows the right tool for right job

In-Memory DB

  • Used mainly for caching
  • Data is stored as key value pairs
  • The values are stored in-memory and are volatile
  • common examples are redis, memcache, etcd(used by kubernetes)

Relational

  • It works like a charm for well structured data with relations
  • Supports ACID properties Works well for applications that needs atomic transactions
  • Horizontal scaling is not supported but most cloud platforms are trying to work around them
  • Famous examples are MySQL & Postgres
  • Well suited for transactional workloads OLTP

NoSQL

DocumentDB

  • Works well for unstructured data
  • Faster reads means increased perfomance
  • Examples are Mongodb, Cassandra
  • DB can be horizontally and vertically scaled

ColumnDB

  • Did I hear analytics, use ColumnDB
  • Because analytics involves comparing two features X and Y and you would be comparing a data in a particular colum
  • They are typically less efficient for inserting new data (Why?)
  • Well suited for OLAP

Graph

  • Works well for Data that's structured in the form of graphs
  • Unlike relational DB the data is defined in the form of node and edges(it's relationshops)
  • Best usecase is for social media application like FB, twitter
  • Example: Neo4j

TimeSeries DBs

  • Timeseries database stores data against a time and other metadata
  • Best example is monitoring applications
  • Data is stored in a hypertable and chunked into columns of metadata & time agaisnt the actual data
  • This Talk clearly explains it https://www.youtube.com/watch?v=eQKbbCg0NqE
  • InfluxDB, TimeseriesDB, Prometheus

Datawarehouse

MultiModel DB

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In-Memory DB
Relational
NoSQL
Graph
TimeSeries DBs
Datawarehouse
MultiModel DB