SQL vs NoSQL

SQL: relational database store data in tables which are formed in rows and columns.

NoSQL:

• key-value

• document

• graph

High level differences

Storage

SQL: table

NoSQL: key-value, document, graph.

Schema

SQL: fixed

NoSQL: dynamic

Querying

SQL: uses SQL (structured query language)

NoSQL: UnQL (unstructured query language).

Scalability

SQL: vertically scalable. Hard to horizontally scale

NoSQL: horizontally scalable.

Reliability or ACID Compliancy (Atomicity, Consistency, Isolation, Durability)

SQL: ACID compliant

NoSQL: sacrifice ACID compliance for performance and scalability.

Ideal Applications

https://www.sitepoint.com/sql-vs-nosql-differences/

Projects where SQL is ideal

• logical related discrete data requirements which can be identified up-front

• data integrity is essential

• standards-based proven technology with good developer experience and support.

Projects where NoSQL is ideal

• unrelated, indeterminate or evolving data requirements

• simpler or looser project objectives, able to start coding immediately

• speed and scalability is imperative.

https://github.com/donnemartin/system-design-primer#sql-or-nosql

• Rapid ingest of clickstream and log data

• Leaderboard or scoring data

• Temporary data, such as a shopping cart

• Frequently accessed ('hot') tables

• Metadata/lookup tables