Which Azure SQL option or open-source database service fits a requirement, and why.
From Ultra Transcenders DP-900 by Tony Rough (publishing soon)
Most choices among Azure relational services come down to the engine an application already uses, how much it depends on instance-level features and how much administration the organisation wants to keep.
| If the requirement is… | Choose | Why |
|---|---|---|
| Full control of the operating system and SQL Server, or OS features unsupported in PaaS | SQL Server on Azure VMs | IaaS with full administrative rights and full compatibility |
| Fastest lift and shift of SQL Server with no changes, and staff to maintain VMs | SQL Server on Azure VMs | Migration is like moving between on-premises servers |
| Move a SQL Server instance and all its databases with minimal changes, without managing VMs | Azure SQL Managed Instance | PaaS with near-100% compatibility with SQL Server Enterprise Edition |
| Cross-database queries and transactions, SQL Server Agent jobs or CLR | Azure SQL Managed Instance | Instance-level features that SQL Database lacks |
| A new cloud application with minimal administration and the highest SLA | Azure SQL Database | Fully managed PaaS, 99.995% availability |
| Several databases with varying, complementary demand | Azure SQL Database elastic pool | Databases share pooled resources to reduce cost |
| One database used intermittently and unpredictably | Azure SQL Database serverless | Automatic scaling, per-second billing, auto-pause |
| Very large database with fast scaling and fast backup and restore | Azure SQL Database Hyperscale | Storage up to 128 TB, decoupled compute and storage |
| An existing MySQL or PostgreSQL app moving to a managed service | Azure Database for MySQL or PostgreSQL Flexible Server | PaaS for the same open-source engine, minimal app changes |
This note is one section of Ultra Transcenders DP-900: Microsoft Azure Data Fundamentals, an independent study guide that explains every topic the exam covers by technology, with comparison tables, diagrams and the common traps, plus a glossary linked to Microsoft Learn.
Publishing soon on Amazon in Kindle and paperback editions.
About the book · DP-900 terms in the glossary · All DP-900 study notes
What each ACID property guarantees in a transactional (OLTP) database, with the classic funds-transfer example.
How extract-transform-load and extract-load-transform differ, and why ELT is common in modern lakehouses.
How OLTP and analytical systems differ in purpose, data shape, queries and users.
How normalisation splits data into one table per entity, linked by keys, so each fact is stored once.
The three Azure SQL options side by side: IaaS or PaaS, compatibility, management and availability.
Storage and access costs, minimum retention periods, Archive rehydration and lifecycle management policies.
The key characteristics of Azure Cosmos DB: schema-agnostic items, automatic indexing, global distribution and low latency.