ElectricSQL vs PowerSync vs Replicache

This post was written by an engineer at QueryPlane. QueryPlane is an app builder for your database: bring your own postgres db and you can create interactive applications to share with other developers, coworkers or even your customers. If you’re interested in trying it out, get started here.

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Sync engines solve the same fundamental problem: keeping data consistent between a server database and client applications. But they differ significantly in scope, architecture, and the tradeoffs they make. ElectricSQL, PowerSync, and Replicache are three of the most prominent options, each taking a distinct approach.

This post compares all three across the dimensions that matter most when choosing a sync engine: sync direction, offline support, conflict resolution, client platforms, backend requirements, and operational complexity.

In this post, we’ll cover:

• Sync direction - Read-only vs. bidirectional
• Architecture - How each engine moves data between server and client
• Offline and conflict resolution - What happens when clients go offline and make changes
• Client platform support - Web, mobile, desktop coverage
• Backend integration - What each tool requires from your server
• Operational complexity - What you need to deploy and maintain
• When to use which - Decision framework based on your use case

Sync direction

The most fundamental difference between these three tools is what they sync and in which direction.

ElectricSQL is a read-path sync engine. It streams data from PostgreSQL to clients in real time using Shapes (filtered subsets of tables). Writes go through your existing backend API—Electric doesn’t handle the write path at all. This is a deliberate design choice that keeps the architecture simple and avoids the complexity of bidirectional sync and conflict resolution.

PowerSync provides full bidirectional sync. Data flows from the server database to client-side SQLite (via Sync Rules and buckets), and client-side writes flow back to the server through a persistent upload queue. Your backend still handles write validation—PowerSync doesn’t bypass your API—but it provides the infrastructure for queuing, retrying, and uploading offline mutations.

Replicache is also bidirectional, but with a different model. Instead of syncing at the database level, it uses a mutator pattern where named operations are applied locally and then sent to the server for authoritative execution. The server pushes back canonical state, and the client rebases unconfirmed mutations on top—similar to how git rebase works.

	ElectricSQL	PowerSync	Replicache
Sync direction	Server → client only	Bidirectional	Bidirectional
Write path	Your existing API	Upload queue → your API	Push mutations → your API
Conflict resolution	N/A (no write sync)	Developer-implemented in backend	Automatic rebase + server authority

Architecture

Each tool has a distinct architecture that shapes how it fits into your stack.

ElectricSQL runs as a standalone Elixir service (Docker container) that connects to PostgreSQL via logical replication. It reads the WAL, filters changes into Shapes, and serves them to clients over HTTP with long polling. Because it uses plain HTTP, Shape data can be cached by CDNs for fan-out to many clients. The architecture is simple: Postgres → Electric service → HTTP → clients. There’s no client-side database—data lives in memory as a materialized Map<key, row>.

PowerSync runs a sync service that also connects to databases via logical replication (for Postgres), change streams (MongoDB), or binlogs (MySQL). But on the client side, PowerSync maintains a full SQLite database. Data is organized into buckets based on Sync Rules, streamed to clients over HTTP streams or WebSockets, and materialized into SQLite tables. Clients query the local SQLite database with full SQL. The architecture is: source database → PowerSync service → streaming → client SQLite.

Replicache has no dedicated server component. It’s a client-side JavaScript library that coordinates with your backend through three endpoints you build: push (send mutations), pull (fetch state), and poke (notify of changes). Data lives in a persistent key-value store in the browser (backed by IndexedDB). The architecture is: your backend ↔ Replicache client library. You build and deploy everything server-side yourself.

Offline support and conflict resolution

Offline capability is often the primary reason teams adopt a sync engine, so it’s worth examining how each tool handles it.

ElectricSQL provides offline reads. Once a Shape’s data is synced to the client, it remains available even without a network connection. But because Electric doesn’t handle writes, there’s no built-in mechanism for queueing offline mutations. If your application needs offline writes, you’d build that yourself—queueing mutations in local storage and sending them when connectivity returns—or pair Electric with another tool. For applications that only need to display data offline (dashboards, reference data, documentation), this is sufficient.

PowerSync provides full offline support for both reads and writes. Client-side SQLite is the source of truth for the local application, and all mutations go through a persistent FIFO upload queue. If the app is offline, writes accumulate in the queue and upload automatically when connectivity returns. The queue survives app restarts and crashes.

Conflict resolution is the developer’s responsibility. PowerSync delivers queued mutations to your backend via the uploadData() function you implement. If two offline clients edit the same row, both mutations eventually reach your API, and your backend decides how to resolve the conflict—last-write-wins, merge, reject, or whatever logic your application requires.

Replicache provides full offline support with a more opinionated conflict resolution model. Mutations are stored persistently and replayed when connectivity returns. The git-like rebase model handles most conflicts automatically: when the server state arrives, unconfirmed local mutations are replayed on top of it. If the server-side mutator produces a different result than the client-side speculation (because of validation failures, authorization checks, or concurrent edits), the server’s result silently replaces the local one.

This rebase model works well when mutations are commutative or when the server is the clear authority. It’s less intuitive for cases where you need explicit conflict resolution UI—like showing the user “your edit conflicts with someone else’s edit, which do you want to keep?”

Client platform support

Platform coverage varies significantly across the three tools.

Platform	ElectricSQL	PowerSync	Replicache
Web (React, Vue, etc.)	Yes	Yes	Yes
React Native	Community	Yes (official)	No
Flutter	No	Yes (official)	No
Swift (native iOS)	No	Yes (official)	No
Kotlin (native Android)	No	Yes (official)	No
Elixir/Phoenix	Yes	No	No
Node.js (server-side)	Yes	Yes (beta)	No

ElectricSQL focuses on TypeScript/JavaScript for web and Elixir for server-side clients. Its web client is framework-agnostic with React-specific hooks available.

PowerSync has the broadest platform coverage. Official SDKs cover Flutter, React Native, Kotlin Multiplatform, Swift, and multiple web frameworks (React, Vue, Svelte, Next.js). This makes it the strongest option for mobile-first or cross-platform applications.

Replicache is browser-only. It’s a JavaScript library that uses browser-specific APIs (IndexedDB, BroadcastChannel for cross-tab sync). If you need native mobile clients, Replicache isn’t an option on its own.

Backend integration

How much server-side work each tool requires is a practical concern that affects adoption cost.

ElectricSQL requires the least backend integration. You deploy the Electric sync service, point it at your Postgres database, and configure Shapes. Your backend doesn’t need any changes—writes continue going through your existing API, and Electric picks up changes from the WAL. The main requirements are that your Postgres instance has wal_level = logical enabled and that the Electric service can connect directly (not through a connection pooler that doesn’t support logical replication).

PowerSync requires moderate backend integration. You deploy the PowerSync service (or use the cloud), configure Sync Rules, and implement the uploadData() function in your client SDK to route mutations to your backend API. Your backend endpoints need to handle the mutations—but they’re the same endpoints your web or mobile app might already use.

Replicache requires the most backend integration. You build three endpoints (push, pull, poke), implement server-side mutators for every mutation your application supports, and manage version tracking for incremental pulls. There’s no server component to deploy—which is both a benefit (no extra infrastructure) and a cost (you build everything). The Replicache documentation provides detailed backend integration guides, including patterns for PostgreSQL.

Backend database support

Database	ElectricSQL	PowerSync	Replicache
PostgreSQL	Yes	Yes	Any (backend-agnostic)
MongoDB	No	Yes (GA)	Any
MySQL	No	Yes (beta)	Any
SQL Server	No	Yes (alpha)	Any

ElectricSQL is Postgres-only. It depends on PostgreSQL’s logical replication and is purpose-built for the Postgres ecosystem. If you’re running Postgres—whether self-hosted, on RDS, Cloud SQL, or another managed provider—this isn’t a limitation. If you’re on MongoDB or MySQL, Electric isn’t an option.

PowerSync supports multiple backend databases: PostgreSQL (GA), MongoDB (GA), MySQL (beta), and SQL Server (alpha). The client side is always SQLite. This flexibility is useful for teams with non-Postgres backends or mixed database environments.

Replicache is backend-agnostic. It doesn’t connect to your database at all—it talks to your API endpoints. You can use any database, any ORM, any backend language.

Operational complexity

ElectricSQL adds one service to your infrastructure: the Electric sync engine, deployed as a Docker container. It needs persistent storage for the Shape cache and a direct connection to Postgres. Electric Cloud eliminates this operational burden entirely for teams that prefer managed infrastructure. Day-to-day operations involve monitoring replication lag and Shape cache size—similar to operating any other CDC-based tool.

PowerSync also adds a sync service, either self-hosted or managed via PowerSync Cloud. The service requires its own storage (MongoDB or Postgres) for bucket state, separate from your source database. Sync Rules add a configuration surface that needs testing and maintenance as your data model evolves. The managed cloud option provides a dashboard for monitoring sync status, connection counts, and data volume.

Replicache adds no server infrastructure—it’s purely a client-side library. But the operational complexity shifts to your backend. You’re responsible for the reliability, performance, and correctness of your push/pull/poke endpoints. Version tracking, mutation idempotency, and incremental state delivery are all your problem. For teams with strong backend engineering capacity, this may be preferable to operating a separate sync service. For teams that want sync as a managed concern, it’s more work.

Pricing

	ElectricSQL	PowerSync	Replicache
Self-hosted	Free (Apache 2.0)	Free (Open Edition)	Free (open-source)
Managed cloud	Free beta (usage-based pricing planned)	From $49/mo (Pro)	N/A
Free tier	Yes (beta period)	Yes (2 GB/mo, 50 connections)	N/A

All three tools are open-source or source-available and can be self-hosted for free. ElectricSQL and PowerSync offer managed cloud services with different pricing models. Replicache has no managed offering—it’s a client library, so there’s nothing to host.

When to use which

Choose ElectricSQL if you’re running PostgreSQL, need real-time data sync to web clients, and your application’s write path already works well. Electric’s read-only sync model is the simplest to adopt—no conflict resolution to think about, no upload queues to manage, no server-side mutators to implement. It’s particularly strong for real-time dashboards, live views, and applications where the CDN-friendly HTTP delivery model helps with scale. See our detailed ElectricSQL post for more.

Choose PowerSync if you need offline write capability on mobile or cross-platform clients. PowerSync’s combination of bidirectional sync, broad SDK coverage (Flutter, React Native, Swift, Kotlin), and multi-database backend support makes it the most versatile option for mobile-first applications. The persistent upload queue and bucket-based partitioning are battle-tested in production at companies in logistics, retail, and field services. See our detailed PowerSync post for more.

Choose Replicache if you’re building a highly interactive web application (think Linear, Figma, or Superhuman-style UX) and want fine-grained control over sync behavior. The git-like rebase model and mutator pattern give you precise control over conflict resolution and optimistic updates. Be aware that Replicache is in maintenance mode—for new projects, evaluate Zero (Replicache’s successor) as well. See our detailed Replicache post for more.

Consider combining tools for complex requirements. ElectricSQL for real-time reads plus your own offline write queue is a valid pattern. The tools aren’t necessarily mutually exclusive—what matters is matching the sync model to your application’s actual needs.

Wrapping up

ElectricSQL, PowerSync, and Replicache represent three different points on the sync engine spectrum. Electric optimizes for simplicity and read-path performance with Postgres. PowerSync provides full bidirectional sync with the widest platform and database coverage. Replicache offers the most control over sync semantics for web applications, with Zero as its evolution.

The right choice depends on your specific requirements: whether you need offline writes, which client platforms you support, what database you run, and how much backend integration you’re willing to take on. For most Postgres-backed web applications that primarily need real-time reads, ElectricSQL’s simplicity is compelling. For mobile-first applications that must work offline, PowerSync is the most complete solution. For web applications demanding the tightest possible UX with fine-grained sync control, Replicache (or Zero) fits best.

For more on the foundational concepts behind these tools—CRDTs, OPFS, local-first architecture—see our post on local-first databases. If you’re running Postgres and evaluating your broader tooling, our posts on top PostgreSQL extensions, managed PostgreSQL cloud providers, and CDC tools for PostgreSQL cover adjacent decisions.