Book Image

Guide to NoSQL with Azure Cosmos DB

By : Gaston C. Hillar, Daron Yöndem
Book Image

Guide to NoSQL with Azure Cosmos DB

By: Gaston C. Hillar, Daron Yöndem

Overview of this book

Cosmos DB is a NoSQL database service included in Azure that is continuously adding new features and has quickly become one of the most innovative services found in Azure, targeting mission-critical applications at a global scale. This book starts off by showing you the main features of Cosmos DB, their supported NoSQL data models and the foundations of its scalable and distributed architecture. You will learn to work with the latest available tools that simplify your tasks with Cosmos DB and reduce development costs, such as the Data Explorer in the Azure portal, Microsoft Azure Storage Explorer, and the Cosmos DB Emulator. Next, move on to working with databases and document collections. We will use the tools to run schema agnostic queries against collections with the Cosmos DB SQL dialect and understand their results. Then, we will create a first version of an application that uses the latest .NET Core SDK to interact with Cosmos DB. Next, we will create a second version of the application that will take advantage of important features that the combination of C# and the .NET Core SDK provides, such as POCOs and LINQ queries. By the end of the book, you will be able to build an application that works with a Cosmos DB NoSQL document database with C#, the .NET Core SDK, LINQ, and JSON.
Table of Contents (13 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Understanding the five consistency levels


Now that we have multiple replicas of our data around the globe, what about data consistency? Cosmos DB provides the following five options:

  • Strong
  • Bounded staleness
  • Session
  • Consistent prefix
  • Eventual

In a replicated dataset, there is always a trade-off between consistency, availability, throughput, and latency. In theoretical computer science, Brewer's theorem (named after computer scientist Eric Brewer), also known as CAP Theorem, says that "

a distributed database can only give two of the three guarantees; consistency, availability, partition tolerance"

. With this context in mind, Cosmos DB offers five different consistency levels, letting us fine-tune our priorities.

Note

Keep in mind that high consistency levels will require more RUs as well.

The following screenshot shows the Default Consistency option in the Azure portal, which allows us to pick the desired consistency level:

For those of you experienced with distributed databases, strong and eventual...