Introduction

ACID

• Atomicity - operations are executed in ‘all or nothing’ manner.
• Consistency - read operations always returns latest state of database.
• Isolation - concurrent operations will yield the same results like ones executed sequentially.
• Durability - committed operations (and data) are stored persistently.

Database types

• Relational (SQL)
• Non-relational (NoSQL)
  • Key-value (Redis, etcd)
  • Document (MongoDB, CouchDB)
  • Multi-model (CosmosDB)
  • Wide-column (BigTable, Cassandra)

Consistency types

• Strong consistency - all nodes contains the same data at the same time
• Weak consistency - nodes might have different data at the same time.
  Changes are propagated to all nodes in background.