@azure/cosmos (TypeScript/JavaScript)
Data plane SDK for Azure Cosmos DB NoSQL API operations — CRUD on documents, queries, bulk operations.
⚠️ Data vs Management Plane
- This SDK (@azure/cosmos): CRUD operations on documents, queries, stored procedures
- Management SDK (@azure/arm-cosmosdb): Create accounts, databases, containers via ARM
Installation
bash
npm install @azure/cosmos @azure/identity
Current Version: 4.9.0 Node.js: >= 20.0.0
Environment Variables
bash
COSMOS_ENDPOINT=https://<account>.documents.azure.com:443/
COSMOS_DATABASE=<database-name>
COSMOS_CONTAINER=<container-name>
# For key-based auth only (prefer AAD)
COSMOS_KEY=<account-key>
Authentication
AAD with DefaultAzureCredential (Recommended)
typescript
import { CosmosClient } from "@azure/cosmos";
import { DefaultAzureCredential } from "@azure/identity";
const client = new CosmosClient({
endpoint: process.env.COSMOS_ENDPOINT!,
aadCredentials: new DefaultAzureCredential(),
});
Key-Based Authentication
typescript
import { CosmosClient } from "@azure/cosmos";
// Option 1: Endpoint + Key
const client = new CosmosClient({
endpoint: process.env.COSMOS_ENDPOINT!,
key: process.env.COSMOS_KEY!,
});
// Option 2: Connection String
const client = new CosmosClient(process.env.COSMOS_CONNECTION_STRING!);
Resource Hierarchy
CosmosClient
└── Database
└── Container
├── Items (documents)
├── Scripts (stored procedures, triggers, UDFs)
└── Conflicts
Core Operations
Database & Container Setup
typescript
const { database } = await client.databases.createIfNotExists({
id: "my-database",
});
const { container } = await database.containers.createIfNotExists({
id: "my-container",
partitionKey: { paths: ["/partitionKey"] },
});
Create Document
typescript
interface Product {
id: string;
partitionKey: string;
name: string;
price: number;
}
const item: Product = {
id: "product-1",
partitionKey: "electronics",
name: "Laptop",
price: 999.99,
};
const { resource } =
await container.items.create<Product>(item);
Read Document
typescript
const { resource } = await container
.item("product-1", "electronics") // id, partitionKey
.read<Product>();
if (resource) {
console.log(resource.name);
}
Update Document (Replace)
typescript
const { resource: existing } = await container
.item("product-1", "electronics")
.read<Product>();
if (existing) {
existing.price = 899.99;
const { resource: updated } = await container
.item("product-1", "electronics")
.replace<Product>(existing);
}
Upsert Document
typescript
const item: Product = {
id: "product-1",
partitionKey: "electronics",
name: "Laptop Pro",
price: 1299.99,
};
const { resource } =
await container.items.upsert<Product>(item);
Delete Document
typescript
await container.item("product-1", "electronics").delete();
Patch Document (Partial Update)
typescript
import { PatchOperation } from "@azure/cosmos";
const operations: PatchOperation[] = [
{ op: "replace", path: "/price", value: 799.99 },
{ op: "add", path: "/discount", value: true },
{ op: "remove", path: "/oldField" },
];
const { resource } = await container
.item("product-1", "electronics")
.patch<Product>(operations);
Queries
Simple Query
typescript
const { resources } = await container.items
.query<Product>("SELECT * FROM c WHERE c.price < 1000")
.fetchAll();
Parameterized Query (Recommended)
typescript
import { SqlQuerySpec } from "@azure/cosmos";
const querySpec: SqlQuerySpec = {
query: "SELECT * FROM c WHERE c.partitionKey = @category AND c.price < @maxPrice",
parameters: [
{ name: "@category", value: "electronics" },
{ name: "@maxPrice", value: 1000 },
],
};
const { resources } = await container.items
.query<Product>(querySpec)
.fetchAll();
Query with Pagination
typescript
const queryIterator = container.items.query<Product>(querySpec, {
maxItemCount: 10, // Items per page
});
while (queryIterator.hasMoreResults()) {
const { resources, continuationToken } = await queryIterator.fetchNext();
console.log(`Page with ${resources?.length} items`);
// Use continuationToken for next page if needed
}
Cross-Partition Query
typescript
const { resources } = await container.items
.query<Product>(
"SELECT * FROM c WHERE c.price > 500",
{ enableCrossPartitionQuery: true }
)
.fetchAll();
Bulk Operations
Execute Bulk Operations
typescript
import { BulkOperationType, OperationInput } from "@azure/cosmos";
const operations: OperationInput[] = [
{
operationType: BulkOperationType.Create,
resourceBody: { id: "1", partitionKey: "cat-a", name: "Item 1" },
},
{
operationType: BulkOperationType.Upsert,
resourceBody: { id: "2", partitionKey: "cat-a", name: "Item 2" },
},
{
operationType: BulkOperationType.Read,
id: "3",
partitionKey: "cat-b",
},
{
operationType: BulkOperationType.Replace,
id: "4",
partitionKey: "cat-b",
resourceBody: { id: "4", partitionKey: "cat-b", name: "Updated" },
},
{
operationType: BulkOperationType.Delete,
id: "5",
partitionKey: "cat-c",
},
{
operationType: BulkOperationType.Patch,
id: "6",
partitionKey: "cat-c",
resourceBody: {
operations: [{ op: "replace", path: "/name", value: "Patched" }],
},
},
];
const response = await container.items.executeBulkOperations(operations);
response.forEach((result, index) => {
if (result.statusCode >= 200 && result.statusCode < 300) {
console.log(`Operation ${index} succeeded`);
} else {
console.error(`Operation ${index} failed: ${result.statusCode}`);
}
});
Partition Keys
Simple Partition Key
typescript
const { container } = await database.containers.createIfNotExists({
id: "products",
partitionKey: { paths: ["/category"] },
});
Hierarchical Partition Key (MultiHash)
typescript
import { PartitionKeyDefinitionVersion, PartitionKeyKind } from "@azure/cosmos";
const { container } = await database.containers.createIfNotExists({
id: "orders",
partitionKey: {
paths: ["/tenantId", "/userId", "/sessionId"],
version: PartitionKeyDefinitionVersion.V2,
kind: PartitionKeyKind.MultiHash,
},
});
// Operations require array of partition key values
const { resource } = await container.items.create({
id: "order-1",
tenantId: "tenant-a",
userId: "user-123",
sessionId: "session-xyz",
total: 99.99,
});
// Read with hierarchical partition key
const { resource: order } = await container
.item("order-1", ["tenant-a", "user-123", "session-xyz"])
.read();
Error Handling
typescript
import { ErrorResponse } from "@azure/cosmos";
try {
const { resource } = await container.item("missing", "pk").read();
} catch (error) {
if (error instanceof ErrorResponse) {
switch (error.code) {
case 404:
console.log("Document not found");
break;
case 409:
console.log("Conflict - document already exists");
break;
case 412:
console.log("Precondition failed (ETag mismatch)");
break;
case 429:
console.log("Rate limited - retry after:", error.retryAfterInMs);
break;
default:
console.error(`Cosmos error ${error.code}: ${error.message}`);
}
}
throw error;
}
Optimistic Concurrency (ETags)
typescript
// Read with ETag
const { resource, etag } = await container
.item("product-1", "electronics")
.read<Product>();
if (resource && etag) {
resource.price = 899.99;
try {
// Replace only if ETag matches
await container.item("product-1", "electronics").replace(resource, {
accessCondition: { type: "IfMatch", condition: etag },
});
} catch (error) {
if (error instanceof ErrorResponse && error.code === 412) {
console.log("Document was modified by another process");
}
}
}
TypeScript Types Reference
typescript
import {
// Client & Resources
CosmosClient,
Database,
Container,
Item,
Items,
// Operations
OperationInput,
BulkOperationType,
PatchOperation,
// Queries
SqlQuerySpec,
SqlParameter,
FeedOptions,
// Partition Keys
PartitionKeyDefinition,
PartitionKeyDefinitionVersion,
PartitionKeyKind,
// Responses
ItemResponse,
FeedResponse,
ResourceResponse,
// Errors
ErrorResponse,
} from "@azure/cosmos";
Best Practices
- Use AAD authentication — Prefer
DefaultAzureCredential over keys - Always use parameterized queries — Prevents injection, improves plan caching
- Specify partition key — Avoid cross-partition queries when possible
- Use bulk operations — For multiple writes, use
executeBulkOperations - Handle 429 errors — Implement retry logic with exponential backoff
- Use ETags for concurrency — Prevent lost updates in concurrent scenarios
- Close client on shutdown — Call
client.dispose() in cleanup
Common Patterns
Service Layer Pattern
typescript
export class ProductService {
private container: Container;
constructor(client: CosmosClient) {
this.container = client
.database(process.env.COSMOS_DATABASE!)
.container(process.env.COSMOS_CONTAINER!);
}
async getById(id: string, category: string): Promise<Product | null> {
try {
const { resource } = await this.container
.item(id, category)
.read<Product>();
return resource ?? null;
} catch (error) {
if (error instanceof ErrorResponse && error.code === 404) {
return null;
}
throw error;
}
}
async create(product: Omit<Product,
"id">): Promise<Product> {
const item = { ...product, id: crypto.randomUUID() };
const { resource } =
await this.container.items.create<Product>(item);
return resource!;
}
async findByCategory(category: string): Promise<Product[]> {
const querySpec: SqlQuerySpec = {
query: "SELECT * FROM c WHERE c.partitionKey = @category",
parameters: [{ name: "@category", value: category }],
};
const { resources } = await this.container.items
.query<Product>(querySpec)
.fetchAll();
return resources;
}
}
Related SDKs
| SDK | Purpose | Install | |
|---|
@azure/cosmos | Data plane (this SDK) | npm install @azure/cosmos | |
@azure/arm-cosmosdb | Management plane (ARM) | npm install @azure/arm-cosmosdb | |
@azure/identity | Authentication | npm install @azure/identity | |
When to Use
This skill is applicable to execute the workflow or actions described in the overview.
Engineering Beyond Boundaries | admin@rootcastle.com