Link to video

What are ACID properties in a database?

                                       SQL vs NoSQL

Advantages of NoSQL :

1. Easier insertion and retrieval
2. More flexible. Schema is changeable.
3. Horizonatally partition already there.
4. Build for metrics, analytics, aggregation.

Disadvantages of NoSQL :

1. Not good for updates.
2. ACID not guaranteed. Hence, financial systems do not use NoSQL.
3. Joins are hard as you need to run through every block. Joins are manual.

Cassandra

Architecture in brief

                                        Cassandra Architeture

Gives us two properties :

• Load Balancing
• Redundancy/ Replication

Distributed consensus

• Quorum - Multiple nodes who are related to a particular query accept a particular value or they come upon or decide on a particular value.