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Azure Cosmos DB vs Azure SQL Database

Azure Cosmos DB and Azure SQL Database are two of the most popular database services offered by Microsoft Azure. While both databases offer many similar features, they have significant differences that make them suitable for different types of applications. In this article, we'll explore the similarities and differences between Azure Cosmos DB and Azure SQL Database, and help you understand which one may be the right choice for your project.


What is Azure Cosmos DB?

Azure Cosmos DB is a globally distributed, multi-model database service offered by Microsoft Azure. It is designed to provide high availability, low latency, and scalability for mission-critical applications. Cosmos DB supports multiple data models including document, key-value, graph, and column-family data models. It also provides APIs for popular programming languages such as .NET, Java, Node.js, Python, and more.


Cosmos DB is a NoSQL database that provides automatic and instant scalability of throughput and storage. It also offers comprehensive SLAs for throughput, latency, consistency, and availability. Cosmos DB is designed to work with Azure services such as Azure Functions, Azure Stream Analytics, and Azure Search.


Advantages:

  1. Allows you to replicate your data across multiple regions to provide low-latency access to your data from anywhere in the world.

  2. Supports multiple data models including document, key-value, graph, and column-family data models. This allows you to use the same database for different types of data.

  3. Azure Cosmos DB provides automatic and instant scalability of throughput and storage. You can scale up or down your throughput and storage without any downtime.

  4. Azure Cosmos DB provides low latency access to your data with single-digit millisecond read and write latencies at the 99th percentile.

Disadvantages:

  1. Can be expensive compared to other database services. The cost depends on the number of requests made to the database and the amount of storage used.

  2. Can be complex to set up and manage compared to other database services.

  3. It requires a good understanding of distributed systems and NoSQL databases.

What companies use Azure Cosmos DB?

  1. Mews

  2. ClearBank

  3. DocuWare

  4. Microsoft-365

  5. Jet.com

  6. Rumble


What is Azure SQL Database?

Azure SQL Database is a fully managed platform as a service (PaaS) database engine that handles most of the database management functions such as upgrading, patching, backups, and monitoring without user involvement. It is a family of managed, secure, and intelligent products that use the SQL Server database engine in the Azure cloud.


Azure SQL Database is always running on the latest stable version of the SQL Server database engine and patched OS with 99.99% availability. It supports modern cloud applications on an intelligent, managed database service that includes serverless computing. Azure SQL Database Hyperscale adapts to changing requirements by rapidly scaling storage up to 100 TB. Its flexible, cloud-native architecture allows storage to grow as needed. You can back up data almost instantaneously and restore your cloud database in minutes—regardless of the size of the data operation.


Advantages:

  1. Integrates with other Azure services such as Azure Active Directory, Azure Key Vault, and more.

  2. Provides high availability with automatic failover to ensure that your application is always available.

  3. Supports SQL queries and provides enterprise-grade security and compliance features.

Disadvantages:

  1. Does not support other data models such as document, key-value, graph, or column-family data models.

  2. Can be expensive compared to other database services. The cost depends on the number of requests made to the database and the amount of storage used.

What companies use Azure SQL Database?

  1. Ataccama

  2. ClearBank

  3. DocuWare

  4. iOLAP

  5. Integrated Control Technology

  6. doubleSlash Net-Business GmbH


The Difference: Azure Cosmos DB vs Azure SQL Database

Factor

Azure Cosmos DB

Azure SQL Database

Type of Database

NoSQL Database

Relational Database

Storage Size

Unlimited storage per database and container.

  • 100 TB for SQL database

  • 8 TB for SQL managed instance

  • 256 TB for SQL virtual machine

Backups

Periodic backup mode (default) – the backup is created at a periodic interval and the data can be restored by creating a request with the support team.

Continuous backup mode – allows you to restore your data to any point of time within the last 30 days.

With long-term backup retention policy, database backups are automatically retained in separate Azure Blob storage containers .

Encryption

CosmosDB encrypts data at rest and the keys are managed by Microsoft. You can also use your own encryption keys .

Supports encryption at rest for Microsoft-managed service side and client-side encryption.

Supports Transparent Data Encryption for server encryption.

The Azure SQL Database supports RSA 2048-bit customer-managed keys in Azure Key Vault.

Replication Methods

It supports replication methods; it ca create copies of the data across multiple regions for high availability and disaster recovery

It supports replication methods but with always 3 replicas available; it ca create upto 3 copies of the data within the same region or across different regions for high availability and disaster recovery

Consistency concepts

It offers various levels of consistency ranging from strong to eventual; it can provide different guarantees on how up-tp-date the data is across multiple replicas

It offers only strong consistency; it can provide the highest guarantee that the data is the same across all replicas at any time.

Scalability

It can scale horizontally by adding more partitions and replicas across multiple regions

It can scale vertically by increasing the computing and memory resources of a single instance

Maintenance

Supports serverless containers that can serve thousands of requests per second.

Supports serverless compute tier for Azure SQL Database.

Supported Programming Languages

.Net

C#

Java

JavaScript

JavaScript (Node.js)

MongoDB client drivers written for various programming languages

Python

.Net

C#

Java

JavaScript (Node.js)

PHP

Python

Ruby

Pricing

Price is based on request units per second and storage (GB per month) of each container or database. Free trial is also available

Price is based on computing and memory resources (vCores) and storage (GB per month) of each instance. The pricing varies depending on the service tier, region and backup retention period.

Data Scheme

It has schema-free data scheme, means it does not enforce any structure on the data stored in its containers

It has schema-based data scheme, means it requires predefined tables and columns for the data stored in its instances.

Server-Side Scripts

JavaScript

Transact SQL

Partitioning Methods

It uses sharding as its partitioning method; it distributes data across multiple partitions based on a partition key

It does not specify its partitioning method

Foreign keys

It does not support foreign keys; it does not enforce any referential integrity constraints between different collections or documents

It supports foreign keys; it can define relationship between different tables or rows and prevent invalid data operations.

Availability

Single-region – 99.99%

Multi-region – 99.999%

SQL database – 99.995% availability

SQL managed instance and SQL virtual machine – 99.99% availability

Transaction concepts

It supports multi-item ACID transactions with snapshot isolation within a partition; it can perform atomic, consistent, isolated ad durable operations on multiple documents or items with the same logical partition

It supports ACID transaction; it can perform atomic, consistent, isolated and durable operations on any data in its instance.

Use cases

Azure Cosmos DB is used for web, mobile, gaming, and IoT application that needs to handle massive amounts of data, reads, and writes at a global scale.

Azure SQL is based on SQL Server engine, you can easily migrate applications and continue to use the tools, languages, and resources that you’re familiar with.

Which one to choose? Azure Cosmos DB or Azure SQL Database

The choice between Azure Cosmos DB and Azure SQL Database ultimately depends on the specific requirements of your application.


If you need a database that can handle a variety of data models and can be scaled globally, Azure Cosmos DB is a good choice. It is designed for low latency and high availability and offers support for multiple data models, making it a good fit for applications that require real-time data access and low latency performance across the globe.


On the other hand, if you have a traditional SQL Server workload and need a relational database that provides high availability, data encryption, automated backups, and disaster recovery, then Azure SQL Database is a better choice. It is a fully managed relational database service that supports SQL Server workloads and provides many of the features of a traditional SQL Server database.


Important: Azure Cosmos DB may come at a higher cost than Azure SQL Database, especially for workloads with smaller data sizes. Therefore, the cost may also be a consideration in your decision-making process.

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