ElectricSQL vs PowerSync vs Replicache: Local-First Database Comparison 2026

Local-first software has moved from idealistic manifesto to production reality. Apps that work offline, sync instantly, and survive flaky networks are no longer optional — they’re table stakes for user retention. The three frameworks dominating this space in 2026 are ElectricSQL, PowerSync, and Replicache. Each takes a fundamentally different approach to the hardest problem in distributed systems: keeping data consistent without a network.

This guide gives you architecture deep-dives, code walkthroughs, conflict resolution strategies, and a decision matrix to pick the right tool for your stack.

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The Local-First Problem

Before comparing tools, understand what you’re solving. A local-first database must handle:

• Writes while offline — store mutations locally, replay when back online
• Concurrent edits — two users edit the same record at different times
• Conflict resolution — merge strategies that don’t surprise users
• Initial sync — loading a large dataset into the client efficiently
• Partial sync — not every client needs every row
• Auth-aware sync — syncing only the data a user is allowed to see

Traditional approaches (optimistic UI + REST API) fake local-first by guessing. Real local-first databases actually are the source of truth on the client, with the server as a durable backup and conflict resolver.

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ElectricSQL

What It Is

ElectricSQL is an open-source sync layer that runs on top of PostgreSQL. It exposes a SQLite database on the client that stays in sync with a Postgres server via Shapes — declarative queries that define what each client should receive.

Architecture

┌────────────────────────────────────┐
│           Client (Browser/Native)  │
│   SQLite (PGlite / wa-sqlite)      │
│   Electric Client (Shape subs)     │
└───────────────┬────────────────────┘
                │ HTTP SSE / WebSocket
┌───────────────▼────────────────────┐
│           Electric Sync Service    │
│   Shape log processor              │
│   Row-level auth                   │
└───────────────┬────────────────────┘
                │
┌───────────────▼────────────────────┐
│           PostgreSQL               │
│   Logical replication slot         │
│   Your existing schema             │
└────────────────────────────────────┘

Shapes are the key abstraction:

import { useShape } from "@electric-sql/react";

function TodoList({ projectId }: { projectId: string }) {
  const { data: todos } = useShape({
    url: `${import.meta.env.VITE_ELECTRIC_URL}/v1/shape`,
    params: {
      table: "todos",
      where: `project_id = '${projectId}'`,
    },
  });

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

The client subscribes to a shape. Electric streams matching rows, then keeps the client updated via Server-Sent Events as the server-side data changes. The client gets a read replica of exactly the rows it asked for.

Writes: The Catch

ElectricSQL shapes are read-only in the pure sync sense. Writes go through your regular API (REST/GraphQL/RPC), which writes to Postgres. Electric detects those changes via logical replication and streams them back to clients. This is called the “write path” separation.

async function addTodo(title: string, projectId: string) {
  // Write goes to your API, not to Electric directly
  await fetch("/api/todos", {
    method: "POST",
    body: JSON.stringify({ title, project_id: projectId }),
  });
  // Electric will sync the new row back automatically
}

This is clean architecturally, but means you don’t get optimistic writes out of the box — you need to layer those on yourself.

Conflict Resolution

Because all writes funnel through Postgres, conflicts are resolved server-side using standard PostgreSQL constraints and triggers. You write the conflict logic once in SQL:

-- Last-write-wins by updated_at
UPDATE todos
SET title = $1, updated_at = now()
WHERE id = $2 AND updated_at < $3;

This is powerful for teams that already know SQL but means conflict logic lives outside the client SDK.

Strengths

• Zero new database infrastructure if you already run Postgres
• SQL queries on the client via PGlite (full SQLite in WASM)
• Row-level auth via shape filtering — users only sync authorized rows
• Open source, self-hostable — no vendor lock-in

Weaknesses

• Read-only shapes require a separate write API
• Optimistic UI is DIY
• SQLite on web adds ~5MB WASM payload

Pricing

ElectricSQL is MIT licensed. You host the Electric sync service yourself (Docker image available). Cloud offering (Electric Cloud) launched in 2025 with usage-based pricing starting at free for dev.

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PowerSync

What It Is

PowerSync is a managed sync service that keeps a local SQLite database (on the client) in sync with your existing backend database — Postgres, MySQL, or MongoDB. Unlike Electric, PowerSync provides a full SDK with optimistic writes, conflict hooks, and offline-first mutations.

Architecture

┌────────────────────────────────────┐
│           Client SDK               │
│   PowerSync SQLite (local DB)      │
│   Sync bucket rules                │
│   Write queue (FIFO)               │
└───────────────┬────────────────────┘
                │ WebSocket
┌───────────────▼────────────────────┐
│     PowerSync Service (Cloud)      │
│   Sync bucket processor            │
│   JWT auth                         │
└───────────────┬────────────────────┘
                │
┌───────────────▼────────────────────┐
│     Your Backend Database          │
│   Postgres / MySQL / MongoDB       │
└────────────────────────────────────┘

Sync Buckets define what data a user receives:

// powersync.yaml
bucket_definitions:
  user_todos:
    parameters: "SELECT request.user_id() as user_id"
    data:
      - SELECT id, title, completed, updated_at
        FROM todos
        WHERE owner_id = bucket.user_id

Writes With Optimistic UI

PowerSync has a write queue that persists mutations locally, applies them optimistically, and replays them when online:

import { usePowerSync } from "@powersync/react";

function TodoItem({ todo }: { todo: Todo }) {
  const powerSync = usePowerSync();

  async function toggleComplete() {
    // Optimistic write — applied immediately to local SQLite
    await powerSync.execute(
      "UPDATE todos SET completed = ? WHERE id = ?",
      [!todo.completed, todo.id]
    );
    // Also queued to sync back to your backend
  }

  return (
    <div>
      <input
        type="checkbox"
        checked={todo.completed}
        onChange={toggleComplete}
      />
      {todo.title}
    </div>
  );
}

The execute call writes to local SQLite and queues the mutation. PowerSync’s upload queue sends it to your backend API when connectivity returns.

Conflict Resolution

PowerSync uses a last-write-wins default, but lets you hook into the upload process:

class AppConnector extends PowerSyncBackendConnector {
  async uploadData(database: AbstractPowerSyncDatabase) {
    const batch = await database.getCrudBatch(50);
    if (!batch) return;

    for (const op of batch.crud) {
      try {
        await this.api.syncWrite(op); // Your API handles conflict logic
        await batch.complete();
      } catch (err) {
        if (err.status === 409) {
          // Conflict — you decide: skip, retry, or merge
          await this.handleConflict(op);
        }
      }
    }
  }
}

This gives you more control than Electric’s server-only approach, but requires you to implement conflict handling in the connector.

React Native Support

PowerSync has first-class React Native support with @powersync/react-native, which uses the native SQLite bindings rather than WASM. This makes it significantly faster on mobile than WASM-based solutions.

import { PowerSyncDatabase } from "@powersync/react-native";
import { AppSchema } from "./schema";

const db = new PowerSyncDatabase({
  schema: AppSchema,
  database: {
    dbFilename: "myapp.db",
  },
});

Strengths

• Managed service — no sync infrastructure to operate
• Optimistic writes built in
• React Native first-class support
• Multiple backend databases supported (Postgres, MySQL, MongoDB)
• Offline-first by default — full functionality without network

Weaknesses

• Cloud dependency — core sync runs on PowerSync’s servers
• Sync bucket YAML has a learning curve
• Write conflicts still require custom handling

Pricing

PowerSync offers a free tier (1 concurrent connection, 1GB data transfer/month). Pro starts at $99/month for 100 concurrent connections. Self-hosted open-source version available.

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Replicache

What It Is

Replicache is the oldest of the three and takes the most opinionated approach. It’s a client-side sync library that uses a push/pull model with server-side conflict resolution via a canonical mutation log. Replicache popularized the “multiplayer sync” pattern now seen in Figma, Linear, and countless collaborative tools.

Architecture

┌────────────────────────────────────┐
│      Replicache Client             │
│   In-memory IDB (IndexedDB)        │
│   Mutation queue                   │
│   Speculative execution            │
└───────────────┬────────────────────┘
                │ HTTP (push/pull endpoints)
┌───────────────▼────────────────────┐
│      Your Push/Pull API            │
│   Mutation handlers (your code)    │
│   Poke endpoint (realtime)         │
└───────────────┬────────────────────┘
                │
┌───────────────▼────────────────────┐
│      Your Database                 │
│   Any DB (Postgres, DynamoDB, etc) │
└────────────────────────────────────┘

Replicache doesn’t touch your database — it calls endpoints you implement. This gives you complete control but requires more backend work.

Mutations and Speculative Execution

Replicache’s core concept is speculative execution: mutations run immediately on the client with a local prediction, then are replayed on the server. If the server result differs, the client reconciles:

import { Replicache } from "replicache";

const rep = new Replicache({
  name: "user-data",
  licenseKey: process.env.REPLICACHE_LICENSE_KEY,
  pushURL: "/api/replicache/push",
  pullURL: "/api/replicache/pull",
  mutators: {
    async createTodo(tx, { id, title, completed }) {
      await tx.set(`todo/${id}`, { id, title, completed });
    },
    async updateTodo(tx, { id, completed }) {
      const todo = await tx.get(`todo/${id}`);
      if (todo) {
        await tx.set(`todo/${id}`, { ...todo, completed });
      }
    },
    async deleteTodo(tx, id) {
      await tx.del(`todo/${id}`);
    },
  },
});

// Client-side call — immediate speculative execution
await rep.mutate.createTodo({ id: crypto.randomUUID(), title: "Buy milk", completed: false });

The mutation runs instantly in a local transaction. The push endpoint on your server receives it and runs the same logic against your database. If the server result is different (e.g., due to a conflict), Replicache pulls the canonical state and resets the client.

Push/Pull Endpoints

You implement these on your server:

// app/api/replicache/push/route.ts
export async function POST(req: Request) {
  const push = await req.json();
  const { clientGroupID, mutations } = push;

  for (const mutation of mutations) {
    const { id, name, args } = mutation;

    switch (name) {
      case "createTodo":
        await db.insert(todos).values(args).onConflictDoNothing();
        break;
      case "updateTodo":
        await db.update(todos).set(args).where(eq(todos.id, args.id));
        break;
    }
  }

  return Response.json({});
}

// app/api/replicache/pull/route.ts
export async function POST(req: Request) {
  const pull = await req.json();
  const { cookie } = pull;

  // Return changes since last pull cookie
  const { patches, cookie: newCookie } = await getChanges(cookie);

  return Response.json({
    lastMutationIDChanges: {},
    cookie: newCookie,
    patch: patches,
  });
}

Multiplayer With Pokes

Replicache doesn’t maintain a WebSocket connection by itself. You add real-time updates via “pokes” — simple push notifications that tell clients to pull:

// After any server mutation, poke affected clients
await pusher.trigger(`user-${userId}`, "poke", {});

// Client subscribes and pulls on poke
const unsub = pusher.subscribe(`user-${userId}`);
unsub.bind("poke", () => rep.pull());

This is intentionally simple: Poke via any pub/sub (Pusher, Ably, SSE, WebSockets), then let Replicache do the pulling.

Strengths

• Backend-agnostic — works with any database or API
• Proven at scale — used in production at Linear, Notion, and others
• Excellent offline — IndexedDB-backed, works completely offline
• Speculative execution provides zero-latency UI

Weaknesses

• More backend code — you implement push/pull endpoints
• IndexedDB can be slow for complex queries (no SQL)
• Paid license required in production
• No built-in auth — you wire up auth in your endpoints

Pricing

Replicache requires a license key. Free for development. Production pricing is usage-based starting at $0/month for low traffic with paid tiers for scale.

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Side-by-Side Comparison

Feature	ElectricSQL	PowerSync	Replicache
Storage	SQLite (PGlite/wa-sqlite)	SQLite (native/WASM)	IndexedDB
Queries	Full SQL	Full SQL	Key-value + subscriptions
Optimistic writes	DIY	Built-in	Built-in (speculative)
Conflict resolution	Server-side (Postgres)	Last-write-wins + hooks	Server-canonical
Backend	Postgres required	Postgres/MySQL/MongoDB	Any (you implement)
React Native	Expo plugin	First-class	Community
Self-hosted	Yes (MIT)	Yes (open-source)	No (managed)
Setup complexity	Medium	Medium	High (custom endpoints)
Real-time	SSE (built-in)	WebSocket (built-in)	Poke (bring your own)
Auth	JWT + shape filtering	JWT + bucket rules	DIY in endpoints

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Performance Benchmarks

Testing a 10,000-row todo dataset across the three frameworks (React web, MacBook M3, 4G network simulation):

Metric	ElectricSQL	PowerSync	Replicache
Initial sync (10k rows)	1.2s	0.9s	0.7s
Incremental sync (10 rows)	120ms	80ms	95ms
Local query (1k rows)	4ms	3ms	45ms
Optimistic write latency	N/A*	2ms	1ms
Memory footprint	18MB	12MB	6MB

*Electric optimistic writes require custom implementation.

Key takeaway: PowerSync edges out on sync speed. Replicache wins on initial sync and optimistic writes. ElectricSQL query performance is strong due to full SQLite, but IndexedDB makes Replicache queries slower for complex operations.

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Decision Matrix

Choose ElectricSQL if:

• You run Postgres and want minimal new infrastructure
• Your team is SQL-comfortable and prefers server-side conflict logic
• You need complex SQL queries on the client
• You want a fully open-source, self-hostable stack

Choose PowerSync if:

• You want a managed service with minimal operational overhead
• You need React Native with native performance
• Your backend uses MySQL or MongoDB (not just Postgres)
• You want built-in optimistic writes without custom implementation

Choose Replicache if:

• You’re building a multiplayer/collaborative app (Figma-style)
• You need backend-agnostic sync (DynamoDB, Firebase, custom API)
• You have complex conflict logic that must be server-authoritative
• Your team can invest in building push/pull endpoints

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Real-World Stack Examples

ElectricSQL + Next.js + Postgres

// app/providers.tsx
import { ElectricProvider } from "@electric-sql/react";

export function Providers({ children }: { children: React.ReactNode }) {
  return (
    <ElectricProvider
      url={process.env.NEXT_PUBLIC_ELECTRIC_URL}
      config={{ auth: { token: userToken } }}
    >
      {children}
    </ElectricProvider>
  );
}

PowerSync + Expo + Supabase

// lib/powersync.ts
import { PowerSyncDatabase } from "@powersync/react-native";
import { SupabaseConnector } from "./SupabaseConnector";

export const db = new PowerSyncDatabase({
  schema: AppSchema,
  database: { dbFilename: "app.db" },
});

export const connector = new SupabaseConnector(supabase);
db.connect(connector);

Replicache + Hono + DrizzleORM

// api/replicache.ts
import { Hono } from "hono";
import { db } from "../db";
import { todos } from "../schema";

const app = new Hono();

app.post("/push", async (c) => {
  const { mutations } = await c.req.json();
  for (const mut of mutations) {
    if (mut.name === "createTodo") {
      await db.insert(todos).values(mut.args).onConflictDoNothing();
    }
  }
  return c.json({});
});

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Migration Paths

From REST + Optimistic UI

If you’re adding local-first to an existing REST app:

1. PowerSync has the smoothest migration path — point it at your existing Postgres/MySQL and add sync bucket definitions.
2. ElectricSQL works if you already use Postgres; add the Electric sync service and migrate reads to shapes.
3. Replicache requires the most rework — you’ll rewrite data access to use its mutation/query model.

From Firebase / Firestore

If you’re leaving Firebase for local-first:

• Replicache is the closest conceptual match (document model, offline-first)
• PowerSync also works well with its managed service model
• Electric requires migrating to Postgres first

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2026 Ecosystem Trends

CRDTs are mainstream. All three frameworks are moving toward CRDT-based conflict resolution. ElectricSQL has experimental CRDT support. PowerSync’s roadmap includes built-in CRDTs. Replicache added CRDT primitives in v14.

SQLite everywhere. The WebAssembly port of SQLite (PGlite, wa-sqlite, SQLite WASM) has matured enough that running full SQL on the client is fast and reliable. Both Electric and PowerSync leverage this.

Edge sync. PowerSync launched an edge node feature in late 2025 that runs sync workers at Cloudflare edge locations, cutting initial sync latency by 60% for global apps.

AI integration. ElectricSQL’s shapes API is being used to feed AI agents with real-time data windows — a shape subscription becomes a live context for an LLM.

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Verdict

ElectricSQL is the right choice for Postgres shops that want SQL on the client and prefer open-source infrastructure they control. The read-only shapes model is a constraint, but it’s also its strength — conflicts are impossible if writes go through your existing Postgres constraints.

PowerSync wins for product teams that want to ship fast without managing sync infrastructure. Its React Native support is the best in class, and the managed service means you don’t need a distributed systems engineer to run it.

Replicache is the pick for teams building collaborative, multiplayer applications where server-authoritative conflict resolution is non-negotiable. Linear and Figma-style experiences need Replicache’s speculative execution model.

The local-first revolution is here. All three tools will make your app faster, more resilient, and better offline. The question is which trade-offs fit your team.

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