Azure Databases¶

Azure SQL¶

Single DB - single database with defined resources
Elastic Pool - multiple databases sharing resources across a pool
Managed Instance - Most compatible with on-prem SQL Server, but managed by Azure
Serverless?
Pricing tiers:
- vCore: corresponds to CPU core, allows fine-grained choice of CPUs and disk space
- DTU: Database Transaction Units cheaper, fewer customizations
Data Migration
- Azure Data Migration Service: establish a connection to on-prem
- Data Migration Assistant: simpler option, allows selecting schema, optionally data, to be migrated
Security
- at-rest data encryption
- Dynamic Data Masking DDM to protect sensitive, PII data

API compatibility with: Azure tables, Cassandra, MongoDB, etcd and Gremlin
- Core (SQL) is recommended for the new applications
Hierarchy: Account > Database > Container > Item
- Account has a globally unique resource name
- throughput can be provisioned at Database or Container levels
- Items are JSON documents
data is sharded into logical partitions using partitioning key
logical partitions are mapped to physical partitions by Azure based on performance requirements
each physical partition writes to 3 replicas known as replica set
- data can be replicated across regions and geo
- allows writes to any replica to be replicated, or write-one-read-many (write only to primary region)
- number of regions for replication can be changed after the database has been created
provisioned and priced by Request Unit RU per second
- e.g. write simple document: 5 RU, simple query: 50 RU
Indexing is by default and indexes all fields
- inverted index can search across documents even with different schemas
- default can be overridden by specifying
  - include.json : paths to include for indexes, attributes: data type, kind (range/hash/spatial), precision
  - exclude.json : processed after include paths
consistency levels are selectable
- strong: all replicas are written for write to complete
- bounded staleness: maximum time write can be inconsistent
- session: consistency guaranteed in the context of the user's session, everyone else has eventual
- eventual: all writes are eventual