tanstack-db

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Overview

TanStack DB is a client-side embedded database layer built on differential dataflow. It maintains normalized collections, uses incremental computation for live queries, provides automatic optimistic mutations, and integrates with TanStack Query for data fetching. Sub-millisecond updates even with 100k+ rows.

Package: @tanstack/react-db Query Integration: @tanstack/query-db-collection Status: Beta (v0.5)

Installation

bash

npm install @tanstack/react-db @tanstack/query-db-collection

Core Concepts

Collections: Normalized data stores wrapping data sources (TanStack Query, Electric, etc.)
Live Queries: Reactive subscriptions with SQL-like query builder
Optimistic Mutations: Automatic instant UI updates with rollback on failure
Differential Dataflow: Only recomputes affected query results on changes

Collections

Creating a Collection

typescript

import { createCollection } from '@tanstack/react-db'
import { queryCollectionOptions } from '@tanstack/query-db-collection'

const todoCollection = createCollection(
  queryCollectionOptions({
    queryKey: ['todos'],
    queryFn: async () => api.todos.getAll(),
    getKey: (item) => item.id,
    schema: todoSchema,
    onInsert: async ({ transaction }) => {
      await Promise.all(
        transaction.mutations.map((mutation) =>
          api.todos.create(mutation.modified)
        )
      )
    },
    onUpdate: async ({ transaction }) => {
      await Promise.all(
        transaction.mutations.map((mutation) =>
          api.todos.update(mutation.modified)
        )
      )
    },
    onDelete: async ({ transaction }) => {
      await Promise.all(
        transaction.mutations.map((mutation) =>
          api.todos.delete(mutation.original.id)
        )
      )
    },
  })
)

Sync Modes

typescript

// Eager (default): Load entire collection upfront. Best for <10k rows.
const smallCollection = createCollection(
  queryCollectionOptions({ syncMode: 'eager', /* ... */ })
)

// On-Demand: Load only what queries request. Best for >50k rows, search.
const largeCollection = createCollection(
  queryCollectionOptions({
    syncMode: 'on-demand',
    queryFn: async (ctx) => {
      const params = parseLoadSubsetOptions(ctx.meta?.loadSubsetOptions)
      return api.getProducts(params)
    },
  })
)

// Progressive: Load query subset immediately, full sync in background.
const collaborativeCollection = createCollection(
  queryCollectionOptions({ syncMode: 'progressive', /* ... */ })
)

Live Queries

Basic Query

typescript

import { useLiveQuery } from '@tanstack/react-db'
import { eq } from '@tanstack/db'

function TodoList() {
  const { data: todos } = useLiveQuery((query) =>
    query
      .from({ todos: todoCollection })
      .where(({ todos }) => eq(todos.completed, false))
  )

  return <ul>{todos.map(todo => <li key={todo.id}>{todo.text}</li>)}</ul>
}

Query Builder API

typescript

const { data } = useLiveQuery((q) =>
  q
    .from({ t: todoCollection })
    .where(({ t }) => eq(t.status, 'active'))
    .orderBy(({ t }) => t.createdAt, 'desc')
    .limit(10)
)

Joins

typescript

const { data } = useLiveQuery((q) =>
  q
    .from({ t: todoCollection })
    .innerJoin(
      { u: userCollection },
      ({ t, u }) => eq(t.userId, u.id)
    )
    .innerJoin(
      { p: projectCollection },
      ({ u, p }) => eq(u.projectId, p.id)
    )
    .where(({ p }) => eq(p.id, currentProject.id))
)

Filter Operators

typescript

import { eq, lt, and } from '@tanstack/db'

// Equality
eq(field, value)

// Less than
lt(field, value)

// AND
and(eq(product.category, 'electronics'), lt(product.price, 100))

With Ordering and Limits

typescript

const { data } = useLiveQuery((q) =>
  q
    .from({ product: productsCollection })
    .where(({ product }) =>
      and(eq(product.category, 'electronics'), lt(product.price, 100))
    )
    .orderBy(({ product }) => product.price, 'asc')
    .limit(10)
)

Optimistic Mutations

Insert

typescript

todoCollection.insert({
  id: uuid(),
  text: 'New todo',
  completed: false,
})
// Immediately: updates all live queries referencing this collection
// Background: calls onInsert handler to sync with server
// On failure: automatic rollback

No Manual Boilerplate

Before (TanStack Query only)	After (TanStack DB)
Manual `onMutate` for optimistic state	Automatic
Manual `onError` rollback logic	Automatic
Per-mutation cache invalidation	All live queries update automatically

Query-Driven Sync (On-Demand)

Live queries automatically generate optimized network requests:

typescript

// This live query...
useLiveQuery((q) =>
  q.from({ product: productsCollection })
    .where(({ product }) => and(eq(product.category, 'electronics'), lt(product.price, 100)))
    .orderBy(({ product }) => product.price, 'asc')
    .limit(10)
)

// ...automatically generates:
// GET /api/products?category=electronics&price_lt=100&sort=price:asc&limit=10

Predicate Mapping

typescript

queryFn: async (ctx) => {
  const { filters, sorts, limit } = parseLoadSubsetOptions(ctx.meta?.loadSubsetOptions)

  const params = new URLSearchParams()
  filters.forEach(({ field, operator, value }) => {
    if (operator === 'eq') params.set(field.join('.'), String(value))
    else if (operator === 'lt') params.set(`${field.join('.')}_lt`, String(value))
  })
  if (limit) params.set('limit', String(limit))

  return fetch(`/api/products?${params}`).then(r => r.json())
}

Performance

Operation	Latency
Single row update (100k sorted collection)	~0.7 ms
Subsequent queries (after sync)	<1 ms
Join across collections	Sub-millisecond

Supported Collection Types

Query Collection - TanStack Query integration
Electric Collection - Electric SQL real-time sync
TrailBase Collection - TrailBase backend
RxDB Collection - RxDB integration
PowerSync Collection - PowerSync sync
LocalStorage Collection - Browser persistence
LocalOnly Collection - In-memory only

API Summary

typescript

import { createCollection, useLiveQuery } from '@tanstack/react-db'
import { queryCollectionOptions } from '@tanstack/query-db-collection'
import { eq, lt, and, parseLoadSubsetOptions } from '@tanstack/db'

Best Practices

Define collections at module level - they're singletons
Choose the right sync mode: eager (<10k), on-demand (>50k), progressive (collaborative)
Use joins instead of view-specific APIs - load normalized collections once
Let TanStack Query handle fetching - DB augments Query, doesn't replace it
Use `parseLoadSubsetOptions` to map live query predicates to API params
Rely on automatic optimistic updates - don't manually manage optimistic state
Use schemas for runtime validation and TypeScript inference
Leverage incremental computation - let the engine handle filtering vs manual .filter()

Common Pitfalls

Creating collections inside components (should be module-level)
Trying to replace TanStack Query entirely (DB builds on top of it)
Using manual .filter() in render instead of live query where clauses
Not providing getKey for proper normalization
Forgetting mutation handlers (onInsert, onUpdate, onDelete) for server sync

Overview

Installation

Core Concepts

Collections

Creating a Collection

Sync Modes

Live Queries

Basic Query

Query Builder API

Joins

Filter Operators

With Ordering and Limits

Optimistic Mutations

Insert

No Manual Boilerplate

Query-Driven Sync (On-Demand)

Predicate Mapping

Performance

Supported Collection Types

API Summary

Best Practices

Common Pitfalls

Autres Skills

tanstack-query

tanstack-table

tanstack-virtual

tanstack-router