ElectricSQL vs Replicache vs TanStack DB: Local-First Sync Frameworks for 2026

Local-first architecture was a niche research concept for most of the 2010s. Ink and Switch published the seminal paper in 2019. Early adopters like Linear, Figma, and Notion proved the UX advantages at scale. By 2025 the pattern graduated from experimental to production-ready, and in 2026 it has become a serious competitor to traditional client-server architectures for collaborative and offline-capable apps.

The core idea: every client has a full or partial replica of relevant data stored locally. Reads are instant (IndexedDB or SQLite lookups). Writes happen locally first, then sync to the server asynchronously. Conflict resolution happens during sync. The server becomes a coordination point rather than a source of truth.

Three frameworks dominate the TypeScript and JavaScript local-first space in 2026: ElectricSQL, Replicache (now Reflect), and TanStack DB. Each takes a different architectural bet. This comparison is based on real 2026 production deployments and internal benchmarks. Our offline-first mobile apps guide covers the broader pattern.

ElectricSQL is the Postgres-native option. You run Postgres on the server (standard Postgres with the Electric logical replication extension). Clients run PGlite (WebAssembly Postgres in the browser) or SQLite locally. Data flows between them via shape subscriptions: declarative queries that the client subscribes to.

Strengths: Real SQL both client and server, Postgres ecosystem compatibility (your existing schema, migrations, ORMs mostly work), mature logical replication, strong typed APIs, Shape subscriptions are concise and powerful.

Weaknesses: Still evolving (major API shifts in 2024 and 2025), requires Postgres on server (not a choice, constraint), CRDT-like conflict resolution is opinionated and may not match your semantics.

Stack: Postgres plus Electric plus a client runtime (Electric Client, PGlite for web, native SQLite for mobile). Works with React, Vue, and vanilla JS.

Performance: Sync latency 100 to 500ms typical. Initial subscription load scales with shape size (can be slow for large datasets; plan shapes carefully). Incremental updates are cheap.

Best for: Apps where you want real SQL on both sides, already running Postgres, willing to adopt a new sync primitive.

Replicache (and its Reflect real-time variant from the same team at Rocicorp) is the most battle-tested local-first framework. It shipped Linear, Magic Eden, and numerous unreleased apps. It works with any backend, any database, any language.

Strengths: Backend-agnostic (bring your own stack), mature and stable, well-documented, deterministic mutator pattern makes conflict resolution predictable, optimistic writes feel instant, strong real-world validation.

Weaknesses: Learning curve for mutators (a conceptual shift from traditional APIs), licensing is commercial past certain scale (per-seat pricing at team level), requires implementing push and pull handlers on your backend.

Stack: Any backend (Node.js, Go, Python, Rust) plus Replicache client library. Uses IndexedDB for client storage. Reflect adds managed server infrastructure for real-time coordination.

Performance: Client-side reads are instant (IndexedDB). Mutator execution under 10ms. Sync latency 100 to 400ms round trip. Handles millions of documents client-side.

Best for: Production apps needing proven reliability, teams with any backend, products where cost of a few cents per seat per month is acceptable.

TanStack DB (from Tanner Linsley, the author of TanStack Query) launched in 2025 as an opinionated take on client-side data plus sync. It integrates deeply with the TanStack ecosystem (Query, Router, Form, Table).

Strengths: Familiar TanStack conventions, reactive SQL queries on client, tight integration with TanStack Query for server state, TypeScript-first API, open source and actively developed.

Weaknesses: Newer (less production validation), sync layer still evolving, smaller ecosystem than Replicache, currently web-first (mobile support in progress).

Stack: TanStack DB client library (IndexedDB-backed), TanStack Query for server interaction, any backend. Sync patterns flexible depending on backend choice.

Performance: Client-side queries are fast (SQL over IndexedDB). Reactivity updates only affected components. Sync perf depends on your chosen transport.

Best for: Teams already invested in TanStack ecosystem, new projects where latest API designs are preferred over proven stability, TypeScript-heavy codebases.

Our TanStack ecosystem guide covers the broader picture.

How each framework handles concurrent edits is the most consequential difference between them.

ElectricSQL: Uses a CRDT-like merge semantics tailored for relational data. Transactional writes maintain consistency. Row-level conflicts typically resolve via last-write-wins with timestamp ordering. Some operations (append-only, counter increments) use specialized CRDT types.

Replicache: Uses deterministic mutators. Each mutation is code that runs both client (optimistically) and server (authoritatively). If the server rejects or modifies the result, the client rebases. This is powerful but requires you to structure mutations carefully.

TanStack DB: Currently offers simple last-write-wins. More sophisticated conflict resolution is on the roadmap. Teams building collaborative apps may need to layer their own CRDT logic (Yjs, Automerge) on top.

Real-time collaboration (multi-user editing): None of these solve this natively. For real-time collab, use Yjs or Automerge alongside your sync framework. See our Yjs vs Automerge vs Liveblocks comparison.

The takeaway: Replicache's mutator model is the most predictable for non-trivial apps. ElectricSQL's CRDT approach works for most apps with some loss of control. TanStack DB requires you to think carefully about concurrent edits.

Schema migrations in local-first apps are painfully hard. Every client has its own copy of the schema and must be migrated on update. Offline clients might have old schemas for weeks. Each framework handles this differently.

ElectricSQL: Uses Postgres migrations server-side. Client schema is inferred from Electric shape subscriptions. Schema version mismatches cause sync errors that need explicit handling. Schema evolution works but is conservative.

Replicache: No client-side schema per se. Data is serialized JSON. You handle schema evolution in mutator code. More flexible but requires discipline to maintain backward compatibility across app versions.

TanStack DB: Schema is declared in TypeScript. Migrations handled via version numbers and migration functions. Relatively straightforward but still evolving.

Best practice across all three: treat schema changes as breaking changes. Support old app versions for at least 2 to 4 weeks to let users update. Test migrations with real stale client data. Document the migration path.

Infra overhead: none of these frameworks absolve you from database migrations. They add a layer of complexity, not subtract.

Real numbers from production deployments in 2025 to 2026:

• Initial sync latency for 50,000 documents: ElectricSQL 3 to 8 seconds, Replicache 1 to 4 seconds, TanStack DB 2 to 6 seconds. Varies heavily with compression and connection speed.
• Incremental sync latency: Sub-second for all three after initial sync on broadband.
• Client memory footprint: ElectricSQL 80 to 200 MB with PGlite (includes WASM Postgres), Replicache 15 to 50 MB, TanStack DB 20 to 60 MB.
• Bandwidth per mutation: All three similar, 500 bytes to 5 KB per mutation depending on document size.
• Concurrent connections per server: ElectricSQL limited by Postgres replication capacity (practical limit 10K to 50K connections). Replicache scales to 1M+ with proper sharding. TanStack DB backend-agnostic.

Bandwidth optimization: all three benefit from shape or query filtering. Don't sync what you don't need. Use compression (all three support it). Prefer incremental loads over full refreshes.

Scale limits: single-region apps with 10K concurrent users are well within reach for all three. Multi-region active-active is harder and is the cutting edge as of 2026.

Decision framework:

• Already running Postgres and want local-first? ElectricSQL. The Postgres-native story is compelling if your schema is relational.
• Building a proven, reliability-first product (think Linear clone)? Replicache or Reflect. Most battle-tested.
• Heavy TanStack user with modern stack? TanStack DB. Consistency across your app.
• Consumer app with simple schema? Any of the three. Pick based on team familiarity.
• Mobile-first app (iOS or Android)? Replicache has native SDKs. ElectricSQL has SQLite story. TanStack DB less mature on mobile.
• Real-time collaborative editing required? None solve this alone. Add Yjs or Automerge on top.

Cost considerations: ElectricSQL is open source (commercial Electric service optional). Replicache is commercial past 30 seats ($0.40 per user per month at time of writing). TanStack DB is MIT open source.

Migration between frameworks: painful. Your data model, sync patterns, and conflict resolution are baked into the framework you choose. Budget 40 to 200 engineering hours for a migration. Choose carefully up front.

Future outlook: we expect 2027 to bring more standardization around sync protocols. Currently each framework has its own wire format. Potential SDK-level compatibility layers are emerging. For now, commit to one and plan to stay.

If you are scoping a local-first architecture for your product, book a free strategy call and we will help you map the tradeoffs.