Cloud Services Cross-Reference: Relational Databases
This document maps relational database services across AWS, Azure, OCI, and Google Cloud. It covers managed open-source engines (MySQL, PostgreSQL), managed commercial engines (SQL Server, Oracle), cloud-native proprietary databases, and migration tooling. Each section includes a cross-reference table followed by differentiator notes.
Managed MySQL
All four clouds offer a fully managed MySQL service running MySQL Community Edition. The key differentiators are the analytics acceleration layer (OCI HeatWave), the serverless variant available on AWS (Aurora), and the edge deployment option (OCI HeatWave on AWS/Azure).
| Feature | AWS RDS for MySQL | Azure Database for MySQL (Flexible Server) | OCI MySQL HeatWave | Google Cloud SQL for MySQL |
|---|---|---|---|---|
| Engine | MySQL Community Edition | MySQL Community Edition | MySQL Community Edition + HeatWave engine | MySQL Community Edition |
| Supported Versions | 8.0, 8.4 | 8.0, 8.4 (minor auto-updated) | 8.0, 8.4, 9.2 (Innovation + LTS tracks) | 5.7, 8.0, 8.4 |
| Service Tiers / Shapes | db.t3/t4g (burstable), db.m6g/r6g (general/memory) | Burstable, General Purpose, Memory Optimized | HeatWave.512GB, HeatWave.1024GB (MySQL.* shapes for non-HeatWave) | Enterprise, Enterprise Plus (shared/dedicated) |
| Storage | Up to 64 TB (gp3/io1/io2) | Up to 16 TB | Up to 512 TB | Up to 64 TB |
| Multi-AZ HA | Multi-AZ (1 standby) or Multi-AZ Cluster (2 standbys) | Same-zone HA or Zone-redundant HA | High Availability (3-node Raft, synchronous) | Regional HA (primary + standby in separate zone) |
| SLA | 99.95% (Multi-AZ) | 99.99% (zone-redundant) | 99.99% | 99.95% (Enterprise), 99.99% (Enterprise Plus) |
| Read Replicas | Up to 5; cross-region supported | Up to 5 read replicas | Up to 18 read replicas; configurable shapes/versions | Up to 10; cross-region supported; HA replicas supported |
| In-database Analytics | No (requires ETL to Redshift) | No | HeatWave: in-memory columnar query accelerator (OLAP on OLTP data, up to 400x faster) | No (requires BigQuery) |
| Serverless | No (use Aurora Serverless v2) | No | No | No (Enterprise Plus auto-scales storage) |
| Encryption at Rest | Yes (KMS) | Yes (AES-256, CMK via Azure Key Vault) | Yes (AES-256, TDE) | Yes (CMEK via Cloud KMS) |
| PITR Retention | Up to 35 days | Up to 35 days | Up to 35 days | Up to 7 days (Enterprise), up to 35 days (Enterprise Plus) |
| Pricing Model | Per vCPU-hour + storage + I/O | Per vCPU-hour + storage + I/O | Per OCPU-hour + storage + HeatWave node-hours | Per vCPU-hour + storage; no I/O charge on Enterprise Plus |
| Multi-cloud Deployment | No | No | Yes (HeatWave on AWS, Azure, OCI) | No |
Notable: OCI MySQL HeatWave is the only managed MySQL service with a native in-database analytics accelerator, machine learning, and generative AI capabilities. This eliminates the ETL step typically required to move data into a separate analytical store. HeatWave Lakehouse extends this to query data in object storage. HeatWave is also deployable on AWS and Azure for customers running MySQL there.
Managed PostgreSQL
PostgreSQL hosting is a competitive space. AWS leads in Aurora's performance claims; Google leads with AlloyDB's HTAP capabilities; Azure offers the broadest version coverage and a new distributed Elastic Clusters option.
| Feature | AWS RDS for PostgreSQL | Azure Database for PostgreSQL (Flexible Server) | OCI PostgreSQL (Database Service) | Google Cloud SQL for PostgreSQL |
|---|---|---|---|---|
| Engine | PostgreSQL Community | PostgreSQL Community | PostgreSQL Community | PostgreSQL Community |
| Supported Versions | 11, 12, 13, 14, 15, 16, 17 | 13, 14, 15, 16, 17, 18 (minor auto-updated) | 14.x (current; 15, 16 roadmap) | 9.6, 10, 11, 12, 13, 14, 15, 16, 17 |
| Service Tiers / Shapes | db.t3/t4g, db.m6g/r6g, db.x2g | Burstable, General Purpose, Memory Optimized | VM.Standard.* shapes (E4, E5, X9) | Enterprise, Enterprise Plus |
| Storage | Up to 64 TB | Up to 64 TB | Up to 320 TB | Up to 64 TB |
| Multi-AZ HA | Multi-AZ (synchronous standby) | Zone-redundant HA or Same-zone HA | Automatic failover (2 standbys using Patroni/Raft) | Regional HA (primary + standby in separate zone) |
| SLA | 99.95% (Multi-AZ) | 99.99% (zone-redundant) | 99.99% | 99.95% (Enterprise), 99.99% (Enterprise Plus) |
| Read Replicas | Up to 5; cross-region supported | Up to 5; cross-region supported | Up to 5 read replicas | Up to 10; cross-region; cascade replicas; HA replicas |
| Horizontal Sharding | No | Elastic Clusters (distributed PostgreSQL, GA 2025) | No | No (use AlloyDB or Spanner instead) |
| Managed Connection Pooling | RDS Proxy (separate service) | PgBouncer built-in | Built-in (connection pooling in service) | Enterprise Plus: managed PgBouncer built-in |
| Vector / AI Extension | pgvector supported | pgvector + Azure AI extension (native embeddings) | pgvector supported | pgvector supported |
| Blue/Green Deployments | Yes | No (uses flexible maintenance windows) | No | No |
| Encryption at Rest | Yes (KMS) | Yes (CMK via Azure Key Vault) | Yes (AES-256, CMK) | Yes (CMEK via Cloud KMS) |
| PITR Retention | Up to 35 days | Up to 35 days | Up to 35 days | Up to 7 days (Enterprise), 35 days (Enterprise Plus) |
| Pricing Model | Per vCPU-hour + storage + I/O | Per vCPU-hour + storage (+ I/O optional) | Per OCPU-hour + storage | Per vCPU-hour + storage; no I/O charge (Enterprise Plus) |
Notable: Azure Database for PostgreSQL Flexible Server introduced Elastic Clusters (distributed PostgreSQL) in GA in 2025, enabling horizontal scale-out for very high throughput workloads. Azure also announced HorizonDB (private preview), a next-generation managed PostgreSQL service. Google Cloud SQL Enterprise Plus offers near-zero downtime maintenance with the 99.99% SLA and includes built-in managed connection pooling (PgBouncer), a feature other clouds charge extra for or omit entirely.
Managed SQL Server
AWS and Google both offer managed SQL Server hosting. Azure is the natural home for SQL Server given Microsoft ownership — it provides three distinct deployment models with varying degrees of compatibility and management. OCI does not offer managed SQL Server as a first-party service.
| Feature | AWS RDS for SQL Server | Azure SQL Database | Azure SQL Managed Instance | Google Cloud SQL for SQL Server | OCI |
|---|---|---|---|---|---|
| Editions Supported | Express, Web, Standard, Enterprise, Developer | N/A (vCore model; General Purpose, Business Critical, Hyperscale tiers) | General Purpose, Business Critical | Web, Standard, Enterprise | Not available |
| SQL Server Versions | 2016, 2017, 2019, 2022 | Always-current (latest stable; no version pinning) | 2019, 2022 | 2017, 2019, 2022 | — |
| Licensing Model | License Included only | License Included or Azure Hybrid Benefit (BYOL) | License Included or Azure Hybrid Benefit (BYOL) | License Included only | — |
| SQL Server Feature Parity | ~95% (some agent/CLR limits) | ~80–85% (no SQL Agent, no cross-DB queries) | ~99% (SQL Agent, CLR, Service Broker, linked servers) | ~95% (with some limits) | — |
| Storage | Up to 16 TB (gp3/io1) | Up to 4 TB (General Purpose), Unlimited (Hyperscale) | Up to 16 TB | Up to 64 TB | — |
| Multi-AZ / HA | Multi-AZ (synchronous) | Zone-redundant (Business Critical / Hyperscale) | Zone-redundant deployment | Regional HA (primary + standby) | — |
| SLA | 99.95% (Multi-AZ) | 99.995% (zone-redundant) | 99.99% | 99.95% (Enterprise), 99.99% (Enterprise Plus) | — |
| Readable Secondaries | No (read replicas promoted, not online) | Business Critical: built-in read replica; Hyperscale: up to 30 named replicas | Business Critical: built-in readable secondary | Read replicas supported | — |
| Geo-Replication / Multi-Region | Cross-region read replicas | Active Geo-Replication (up to 4 secondaries); Failover Groups | Failover Groups (instance-level) | Cross-region read replicas | — |
| Serverless | No | Yes (Azure SQL Database Serverless tier — auto-pause/resume) | No | No | — |
| Pricing Model | Per vCPU-hour + storage + I/O | vCore + storage + (optional) I/O; DTU model also available | Per vCPU-hour + storage | Per vCPU-hour + storage; no I/O charge (Enterprise Plus) | — |
Notable: Azure SQL Database is the only offering with a Serverless tier (auto-pauses during inactivity, resumes on connection), making it cost-effective for intermittent workloads. Azure SQL Managed Instance provides the highest SQL Server compatibility for lift-and-shift migrations, including SQL Agent, CLR, and native backup/restore to .bak files. Azure Hybrid Benefit allows existing SQL Server License Assurance customers to bring their licenses to Azure, reducing cost by up to 55% on top of Reserved Instance pricing.
Managed Oracle Database
AWS offers managed Oracle hosting as a PaaS service. OCI provides two first-party paths: a self-managed equivalent (Base Database Service) and fully autonomous operation (Autonomous Database). Azure and Google Cloud do not offer managed Oracle Database as first-party services, though Oracle has multicloud interconnect agreements with both Azure and Google.
| Feature | AWS RDS for Oracle | OCI Base Database Service | OCI Autonomous Database | Azure (via Oracle DB@Azure) | GCP (via Oracle DB@Google) |
|---|---|---|---|---|---|
| Nature | Managed PaaS (Oracle software on RDS infrastructure) | Managed Oracle DB on OCI VMs/bare metal (self-managed) | Fully autonomous PaaS (self-patching, self-tuning, self-securing) | Oracle-managed Exadata running in Azure DCs | Oracle-managed Exadata running in Google DCs |
| Oracle Editions | Standard Edition 2, Enterprise Edition | SE2, Enterprise Edition (High Performance, Extreme Performance) | Enterprise Edition Extreme Performance (embedded) | EE Extreme Performance (Exadata-based) | EE Extreme Performance (Exadata-based) |
| Versions | 19c, 21c | 19c, 21c (26ai preview) | 19c (auto-upgraded by Oracle) | 19c | 19c |
| Licensing | License Included or BYOL | BYOL (Enterprise); License Included options available | Included in service price | BYOL | BYOL |
| RAC | No | Yes (2-node RAC on VM DB systems) | No (serverless scales transparently) | Yes (Exadata-based) | Yes (Exadata-based) |
| Data Guard / HA | Multi-AZ (synchronous standby) | Data Guard (synchronous/asynchronous); Active Data Guard (EE Extreme Performance) | Autonomous Data Guard: local + cross-region standby; auto-failover in ~30 seconds | Active Data Guard | Active Data Guard |
| SLA | 99.95% | 99.95% | 99.995% (with Autonomous Data Guard) | 99.95% | 99.95% |
| Self-Patching | No (managed patching window) | No (DBA-initiated) | Yes (zero-downtime patching, transparent) | No | No |
| Self-Tuning | No | No | Yes (automatic indexing, partitioning, statistics) | No | No |
| Workload Types | General (OLTP/batch) | General (OLTP/batch/DW) | ATP (OLTP), ADW (analytics/data warehouse), AJD (JSON), APEX Service | General | General |
| Serverless / Elastic Scale | No | No (scale requires VM resize) | Yes (Serverless: scale OCPUs per second) | No | No |
| Storage | Up to 64 TB (EBS) | Up to 40 TB per VM (tiered) | Unlimited (auto-growing, Exadata storage) | Exadata-class storage | Exadata-class storage |
| Dedicated Infrastructure | No | Yes (dedicated VMs/bare metal) | Yes (Autonomous Database on Dedicated Exadata) | Yes | Yes |
| Pricing Model | Per OCPU-hour + storage (BYOL discount available) | Per OCPU-hour + storage | OCPU-hour + storage TB-month (Serverless); fixed Exadata cost (Dedicated) | Oracle subscription pricing | Oracle subscription pricing |
Notable: OCI Autonomous Database is unique across all four clouds. No other provider offers a database that autonomously handles patching, tuning, security hardening, and scaling without DBA intervention. The service delivers Oracle Enterprise Edition Extreme Performance capabilities (Active Data Guard, partitioning, compression, in-memory) bundled into a single price. Oracle Database@Azure and Oracle Database@Google Cloud are joint offerings where Oracle hardware runs inside Azure/Google data centers, connected to native cloud services via a low-latency private interconnect — they are managed by Oracle, not by the cloud provider.
Cloud-Native / Proprietary Relational Databases
Each cloud provider has at least one proprietary relational database designed specifically for cloud-scale workloads that cannot be mapped directly to an existing open-source or commercial engine.
| Feature | Amazon Aurora | Azure SQL (Hyperscale / Serverless) | OCI Autonomous Database | Google AlloyDB | Google Spanner |
|---|---|---|---|---|---|
| Compatible Engine | MySQL 8.0 / PostgreSQL 16 | SQL Server (T-SQL) | Oracle SQL / PL/SQL | PostgreSQL 15/16 | Proprietary SQL (ANSI-compatible) |
| Architecture | Distributed storage layer decoupled from compute; 6-way replication across 3 AZs | Hyperscale: tiered storage with page servers; Serverless: auto-pause compute | Exadata infrastructure; auto-management layer | Distributed storage with columnar engine + row engine; ML-driven vacuum/indexing | Globally distributed; TrueTime for external consistency |
| Max Storage | 256 TiB (auto-growing; increased July 2025) | Hyperscale: 100 TB | Exadata-class (effectively unlimited in Dedicated) | 64 TB per cluster | Petabytes (horizontal sharding) |
| Read Scale | Up to 15 Aurora Replicas; low-latency replica lag | Hyperscale: up to 30 named replicas | Autonomous Data Guard readable standby | Up to 20 read pool nodes | Unlimited read replicas per region |
| Multi-Region | Aurora Global Database (RPO: <1s, RTO: <1 min) | Active Geo-Replication / Failover Groups | Cross-Region Autonomous Data Guard | Cross-region read replicas (preview) | Built-in multi-region; single-instance spans regions |
| Serverless | Aurora Serverless v2 (scales per second, $0.12/ACU-hr) | Azure SQL Serverless (auto-pause/resume; billed per vCore-second active) | ADB Serverless (scales OCPUs per second) | No (AlloyDB Omni for off-cloud) | Yes (Spanner autoscaler or Serverless option) |
| HTAP (Mixed OLTP+OLAP) | Limited (requires Aurora zero-ETL to Redshift) | No | Yes (HeatWave on OCI ATP + ADW) | Yes (columnar engine accelerates analytics 100x) | Partial (optimized for global OLTP; analytics via Spanner Federation) |
| SLA | 99.99% (multi-region Global Database) | 99.995% (zone-redundant Business Critical) | 99.995% (Autonomous Data Guard) | 99.99% | 99.999% (multi-region) |
| Performance Claim | 5x MySQL throughput; 3x PostgreSQL throughput | Rapid scale-out reads via page servers | 66% more efficient DBA teams (IDC) | 4x faster than standard PostgreSQL (OLTP); 100x faster (analytics) | Sub-10ms latency globally for most workloads |
| Offline / Hybrid Deployment | No | No | Exadata Cloud@Customer (on-prem) | AlloyDB Omni (downloadable; runs anywhere; $69.95/vCPU/month) | Spanner emulator (dev only); no production on-prem |
| Pricing Model | Per ACU-hour (Serverless) or per instance-hour + $0.10/GB storage | Per vCPU-second (Serverless) or per vCore-hour (provisioned) | Per OCPU-hour + storage (Serverless) | Per vCPU-hour + storage (no I/O charges) | Per node-hour or Processing Units + storage + operations |
Notable differentiators:
- Amazon Aurora delivers MySQL/PostgreSQL compatibility at higher performance through a purpose-built distributed storage engine. Aurora Serverless v2 fine-grained scaling (0.5 ACU increments, billed per second) makes it cost-effective for variable workloads. Aurora Global Database enables active-passive multi-region with sub-second RPO.
- Azure SQL Hyperscale decouples compute from storage through a page-server architecture, enabling near-instantaneous database snapshots, rapid scaling up to 100 TB, and up to 30 named readable secondary replicas for heavy reporting workloads.
- OCI Autonomous Database remains unique: the only cloud database with fully autonomous lifecycle management covering patching (zero downtime), tuning (automatic index creation and drop), security (automatic encryption key rotation), and scaling (OCPU scaling with no connection drop). The 99.995% SLA with Autonomous Data Guard covers both planned and unplanned downtime.
- Google AlloyDB is PostgreSQL-compatible with a disaggregated storage architecture and a built-in columnar engine for analytical acceleration. AlloyDB Omni allows the same engine to run on-premises or on other clouds, a unique portability option for PostgreSQL workloads.
- Google Spanner is in a category of its own: the only cloud database that provides external consistency (linearizability) across a globally distributed deployment as a standard feature. It does not map to any open-source engine. Use cases are applications requiring global scale with strong consistency guarantees where the cost of global Spanner nodes is justified.
Database Migration Services
| Feature | AWS Database Migration Service (DMS) | Azure Database Migration Service | OCI Database Migration Service | Google Database Migration Service |
|---|---|---|---|---|
| Service Type | Fully managed | Fully managed | Fully managed (orchestrates ZDM, GoldenGate, Data Pump) | Fully managed |
| Supported Sources | Oracle, SQL Server, MySQL, PostgreSQL, MongoDB, DB2, SAP ASE, and others | SQL Server, MySQL, PostgreSQL, Oracle, MongoDB, and others | Oracle (on-prem/OCI Classic), MySQL, PostgreSQL | MySQL, PostgreSQL, Oracle (for Cloud SQL/AlloyDB targets) |
| Supported Targets | All RDS engines, Aurora, DynamoDB, Redshift, S3 | Azure SQL DB, SQL MI, MySQL, PostgreSQL, Cosmos DB | Autonomous Database, Base DB, MySQL HeatWave | Cloud SQL (MySQL, PostgreSQL, SQL Server), AlloyDB |
| CDC (Change Data Capture) | Yes (log-based) | Yes (online migrations) | Yes (via GoldenGate for Oracle; binlog for MySQL) | Yes (native CDC for homogeneous migrations) |
| Homogeneous Migration Cost | Billed per replication instance-hour | Standard tier: free; Premium tier: per vCore-hour | Free (OCI DMS service itself is free; GoldenGate/ZDM costs apply) | Free for homogeneous migrations; first 50 GB backfill free |
| Heterogeneous Migration | Yes (schema conversion via AWS SCT) | Yes (SSMA for SQL Server/Oracle to Azure SQL) | Yes (SQL Developer, Cloud Premigration Advisor, ZDM) | Yes (Gemini AI-assisted stored procedure conversion) |
| Zero-Downtime / Online | Yes (CDC-based online migration) | Yes (Premium tier online migration) | Yes (GoldenGate-based zero downtime) | Yes (CDC-based continuous replication) |
| Infrastructure to Manage | Replication instance (EC2-based) | None (serverless) | None (orchestrated service) | None (serverless) |
| Oracle-to-PostgreSQL | Yes (DMS + Schema Conversion Tool) | Yes (SSMA for Oracle) | Limited (focused on Oracle-to-Oracle paths) | Yes (with Gemini-assisted code conversion) |
| Real-time Replication | Limited (DMS CDC has known performance ceiling at scale) | Online migrations (DMS Premium) | Sub-second via OCI GoldenGate | Yes |
| Assessment / Pre-migration | AWS Schema Conversion Tool (SCT) | Azure Database Migration Assessment | Cloud Premigration Advisor Tool (CPAT) | Database Migration Assessment (for Oracle conversions) |
Notable:
- OCI GoldenGate is Oracle's flagship real-time data replication product, available as a fully managed service on OCI. It provides sub-second latency CDC and bidirectional replication, supporting Oracle-to-Oracle as well as heterogeneous sources. It is the only migration service where the GoldenGate software license is bundled into the OCI service price. Running GoldenGate on AWS or Azure requires a separate Oracle license.
- Google DMS is the only service offering AI-assisted (Gemini) conversion of database-resident code (stored procedures, triggers, functions) for Oracle-to-PostgreSQL migrations as of 2025.
- AWS DMS is the most mature service for general heterogeneous migrations and integrates with the AWS Schema Conversion Tool for automated schema translation. However, it requires a managed replication instance (EC2-based) that must be sized and monitored separately.
- Azure DMS Standard tier is free for offline migrations, making it the lowest-cost entry point for SQL Server and MySQL migrations to Azure.
High Availability and Multi-Region Summary
| Capability | AWS | Azure | OCI | Google Cloud |
|---|---|---|---|---|
| Zone-redundant HA | Multi-AZ (synchronous standby; auto-failover) | Zone-redundant (synchronous; auto-failover) | High Availability (3-node for MySQL HeatWave; Data Guard for Oracle) | Regional HA (primary + standby in separate zone) |
| Cross-region read replicas | Yes (RDS MySQL, PostgreSQL, Oracle, MariaDB; Aurora) | Yes (Azure SQL: Active Geo-Replication; MySQL/PostgreSQL: geo-replicas) | Yes (OCI MySQL read replicas; Oracle: cross-region Data Guard) | Yes (Cloud SQL, AlloyDB; cross-region read pools) |
| Auto-failover | Yes (Multi-AZ; Aurora) | Yes (Failover Groups with listener DNS) | Yes (Autonomous Data Guard auto-failover in ~30s) | Yes (Cloud SQL HA; AlloyDB HA) |
| Global / Multi-region active | Aurora Global Database (active-passive) | Active Geo-Replication (up to 4 readable secondaries) | Cross-Region Autonomous Data Guard | Spanner (active-active globally distributed) |
| Max HA SLA | 99.99% (Aurora Global Database) | 99.995% (Azure SQL zone-redundant) | 99.995% (ADB with Autonomous Data Guard) | 99.999% (Spanner multi-region) |
| Planned downtime coverage | Not covered by SLA | Not covered by SLA | Covered by ADB SLA (zero-downtime patching) | Not covered by SLA |
| RDS/SQL Automatic Backup Retention | Up to 35 days | Up to 35 days | Up to 60 days (Autonomous Recovery Service) | Up to 35 days (Enterprise Plus) |
References
- Amazon RDS — Managed Relational Database
- Amazon RDS for MySQL
- Amazon RDS for PostgreSQL
- Amazon RDS for Oracle
- Amazon RDS for SQL Server
- Amazon Aurora
- AWS DMS — Database Migration Service
- RDS Oracle — Supported Versions
- Azure SQL Database
- Azure Database for MySQL
- Azure Database for PostgreSQL
- What is Azure SQL — IaaS vs PaaS comparison
- Azure Database for PostgreSQL — Supported Versions
- Azure Active Geo-Replication
- Oracle Autonomous Database
- OCI Base Database Service FAQ
- OCI Database Migration Service
- Autonomous Database — 99.995% SLA with Autonomous Data Guard
- Oracle MySQL HeatWave
- Google Cloud SQL
- Cloud SQL Editions Overview — MySQL
- Cloud SQL Editions Overview — PostgreSQL
- Google AlloyDB for PostgreSQL — Overview
- Google Cloud Spanner
- Google Database Migration Service