Cosmos DB in a Nutshell

A Brief History of Cosmos DB (Or: How We Got Here)

Once upon a time, databases were simple. You had SQL, and everything was structured, relational, and predictable. But then developers wanted more. More speed. More scalability. More ways to store data that didn’t always fit neatly into tables.

Enter NoSQL databases, which came along like a group of rebellious teenagers, saying, “Who needs schemas anyway?” Microsoft saw the chaos, rubbed its hands together, and in 2017 officially introduced Azure Cosmos DB to bring order to the NoSQL world—while still keeping the chaos fun.

Cosmos DB is Microsoft’s globally distributed, multi-model database service that lets you store data with millisecond response times and automatic scaling. Think of it like a pizza delivery service that can reach any part of the world instantly, except instead of pizza, it’s your data. (Okay, we all wish it was pizza.)

Why Should You Care About Cosmos DB?

Good question! Here’s why Cosmos DB is awesome:

• Multi-model support – You can store your data as documents (MongoDB-style), key-value pairs, graphs, or tables.
• Global distribution – Your data can be replicated across multiple Azure regions automatically.
• Elastic scalability – It scales horizontally, so you can handle insane amounts of data without breaking a sweat.
• Low-latency reads and writes – Microsoft claims single-digit millisecond response times. That’s fast enough to make even your internet provider jealous.
• Fully managed – You don’t have to worry about backups, patching, or maintenance. Just store your data and focus on building cool stuff.

Cosmos DB in Action: Code Examples

Alright, let’s get our hands dirty with some actual Cosmos DB code. We’ll use C# with the .NET SDK to interact with Cosmos DB. But don’t worry, the same principles apply to other languages like Python, JavaScript, and Java.

1. Setting Up Your Cosmos DB Client

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using Microsoft.Azure.Cosmos;
using System;
using System.Threading.Tasks;

class Program
{
    private static readonly string EndpointUri = "https://your-cosmosdb-account.documents.azure.com:443/";
    private static readonly string PrimaryKey = "your-primary-key-here";
    private static CosmosClient cosmosClient;

    static async Task Main(string[] args)
    {
        cosmosClient = new CosmosClient(EndpointUri, PrimaryKey);
        Console.WriteLine("Connected to Cosmos DB!");
    }
}

2. Creating a Database and a Container

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var database = await cosmosClient.CreateDatabaseIfNotExistsAsync("MyDatabase");
var container = await database.Database.CreateContainerIfNotExistsAsync("MyContainer", "/id");
Console.WriteLine("Database and container created!");

3. Inserting Data

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var item = new { id = "1", name = "Captain Data", type = "Hero" };
await container.Container.CreateItemAsync(item, new PartitionKey(item.id));
Console.WriteLine("Item inserted!");

4. Querying Data

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var query = "SELECT * FROM c WHERE c.type = 'Hero'";
var iterator = container.Container.GetItemQueryIterator<dynamic>(query);
while (iterator.HasMoreResults)
{
    foreach (var item in await iterator.ReadNextAsync())
    {
        Console.WriteLine(item);
    }
}

5. Updating Data

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var updatedItem = new { id = "1", name = "Captain Data", type = "Superhero" };
await container.Container.ReplaceItemAsync(updatedItem, updatedItem.id);
Console.WriteLine("Item updated!");

6. Deleting Data

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await container.Container.DeleteItemAsync<object>("1", new PartitionKey("1"));
Console.WriteLine("Item deleted!");

Key Ideas

References

1. Azure Cosmos DB Documentation
2. Cosmos DB SDK for .NET
3. Azure Pricing Calculator