Using ElectricSQL to Build a Local-First App

ElectricSQL represents a fundamental shift in how developers think about data synchronization in web and mobile applications. By bringing the database closer to the user and handling sync as a first-class concern, ElectricSQL enables applications that feel instant, work offline, and stay synchronized across all devices.

This guide explores how to leverage ElectricSQL to build local-first applications that deliver exceptional user experiences while maintaining the reliability of server-side data storage. Our web development services team regularly implements these patterns for clients requiring real-time collaboration features.

What Is ElectricSQL?

ElectricSQL is an open-source Postgres sync engine that enables developers to build local-first and reactive applications with unprecedented ease. The platform handles the complex challenges of data synchronization, including partial replication, fan-out, and reliable data delivery, allowing developers to focus on building their application's core functionality rather than managing sync logic.

The fundamental insight behind ElectricSQL is that modern applications require a fundamentally different approach to data management. Traditional web applications rely on constant network connectivity, with every user interaction requiring a round-trip to the server. This approach introduces latency, creates poor user experiences during connectivity issues, and places unnecessary load on server infrastructure. ElectricSQL reimagines this architecture by placing a local database in the client application and synchronizing changes bidirectionally in the background.

The Local-First Paradigm

The local-first paradigm represents the next frontier in front-end development, offering significant improvements in user experience, developer experience, and application architecture. Sync-based applications like Linear and Figma have demonstrated that local-first approaches yield applications that are instant to use and naturally collaborative, eliminating stale data, loading spinners, and manual data wiring.

Local-first applications store data locally on the user's device, enabling immediate access regardless of network connectivity. Changes are made against this local store and then synchronized to the server in the background. This architecture provides several key benefits:

• Performance improves dramatically because data access happens locally rather than requiring network requests
• Offline functionality allows applications to remain functional during network outages
• Collaboration becomes seamless when multiple users can work with the same data simultaneously

For teams implementing AI automation solutions, local-first architecture provides a robust foundation for building intelligent applications that function reliably across varying network conditions.

Building with TanStack DB

TanStack DB extends TanStack Query with local-first synchronization capabilities, creating an optimal end-to-end sync stack when paired with ElectricSQL. The combination leverages TanStack's existing patterns for data fetching and mutations while adding local database storage, live queries, and transactional writes.

Collections

Collections are the fundamental data containers in TanStack DB, representing typed sets of objects that can be populated from various sources. The collection abstraction allows applications to treat data from different sources uniformly.

Query Collections fetch data using TanStack Query's existing mechanisms:

const todoCollection = createCollection(
 queryCollectionOptions({
 id: 'fetch-todos',
 queryKey: ['todos'],
 queryFn: async () => await api.get('/todos'),
 getKey: (item) => item.id,
 schema: todoSchema,
 queryClient,
 })
)

Sync Collections automatically maintain data freshness through ElectricSQL:

const electricTodoCollection = createCollection(
 electricCollectionOptions({
 id: 'sync-todos',
 shapeOptions: {
 url: 'http://localhost:3003/v1/shape',
 params: { table: 'todos' },
 },
 getKey: (item) => item.id,
 schema: todoSchema,
 })
)

Live Queries

Live queries provide reactive access to collection data, automatically updating components when underlying data changes. Built on differential dataflow principles, live queries achieve sub-millisecond performance even for complex queries.

Transactional Mutations

TanStack DB's mutation system extends TanStack Query's patterns with transactional capabilities and tighter integration with sync machinery. Mutations apply writes immediately to local optimistic state while synchronizing changes to the server in the background.

Direct Collection Operations:

const completeTodo = todoCollection.update(todo.id, (draft) => {
 draft.completed = true
})

Transactional Mutations Across Collections:

const createUserWithWorkspace = createOptimisticAction({
 (loginName) => {
 const userId = crypto.randomUUID()
 const workspaceId = crypto.randomUUID()

 userCollection.insert({ id: userId, name: loginName })
 workspaceCollection.insert({ id: workspaceId, name: 'Default' })
 membershipCollection.insert({ role: 'owner', userId, workspaceId })
 },
 mutationFn: async (_loginName, { transaction }) => {
 await api.post('/create-user-workspace', transaction)
 }
})

If any part of a transaction fails, all changes roll back automatically, ensuring data consistency even when complex operations involve multiple collections.

Best Practices for Local-First Development

Incremental Adoption Strategy

One of ElectricSQL's most compelling features is its support for incremental adoption. Rather than requiring a complete application rewrite, teams can adopt local-first patterns gradually:

1. Wrap existing API calls in query collections, maintaining current behavior
2. Modify components to read from collections rather than direct API calls
3. Convert writes to use TanStack DB mutations
4. Migrate collections from query-based to sync-based for real-time updates

This approach provides immediate benefits with minimal risk, allowing teams to validate ElectricSQL's value before committing fully. Our web development services team specializes in modernizing legacy applications with local-first patterns.

Performance Optimization

• Shape Design: Sync only the data each client needs, avoiding unnecessary columns or rows
• Query Structure: Normalized data with appropriate foreign keys enables efficient joins
• Caching Strategies: Balance memory usage against query performance per collection

Handling Conflicts and Errors

• ElectricSQL tracks changes by transaction ID, allowing local state to rebase over concurrent writes
• Failed writes trigger automatic optimistic state rollback
• Network issues queue changes locally, syncing automatically when connectivity returns

For enterprise applications requiring robust automation capabilities, integrating AI automation services with local-first architecture creates powerful, responsive experiences that work reliably regardless of network conditions.

Sources

1. ElectricSQL Official Documentation - Comprehensive documentation covering Electric's core sync engine, integration with TanStack DB, and various use cases
2. ElectricSQL Quickstart Guide - Step-by-step tutorial for setting up Electric with TanStack DB
3. Local-First Sync with TanStack DB - Technical deep-dive into TanStack DB integration
4. Using ElectricSQL to Build a Local-First Application - LogRocket - Practical implementation guide with code examples