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Convex vs Harper (formerly HarperDB)

Convex: Reactive TypeScript backend with a transactional document database, server functions and live queries. Harper (formerly HarperDB): Node.js runtime that fuses database, cache, app logic and MQTT/WebSocket messaging in one process.

key differences

  • Licensing: Convex is source-available (FSL-1.1-Apache-2.0 (backend); Apache-2.0 client); Harper (formerly HarperDB) is open source (permissive) (Apache License 2.0 (core); Elastic License 2.0 (Harper Pro)).
  • Horizontal scaling is none in Convex and addon in Harper (formerly HarperDB).
  • Transactions: Convex offers full ACID; Harper (formerly HarperDB) offers limited.
  • Only Convex has full-text search, change data capture, stored procedures.
  • Only Harper (formerly HarperDB) has joins, ttl / expiry, in-memory, role-based access.
  • Convex has a serverless option; Harper (formerly HarperDB) does not.

choose convex for

  • +Realtime collaborative SaaS apps
  • +AI chat and agent apps with vector search
  • +Startups replacing a hand-built API plus cache
  • +Apps scaffolded by AI coding tools

best at · OLTP, Vector search, RAG

choose harperdb for

  • +Edge caching and API acceleration in front of slower origins
  • +Real-time apps needing MQTT or WebSocket fan-out
  • +Geo-distributed application backends
  • +Vector lookups next to application logic

best at · Cache, Edge, Pub/Sub

ConvexReactive TypeScript backend with a transactional document database, server functions and live queries.
Harper (formerly HarperDB)Node.js runtime that fuses database, cache, app logic and MQTT/WebSocket messaging in one process.
overview
Primary model
Document
Document
Also supports
Vector, Search Engine
Key-Value, Vector
Type
Backend platform
Backend platform
Status
Active
Active
Developer
Convex, Inc.
HarperDB, Inc.
First release
2022
2017
Latest version
1.48.0 (npm client) (Oct 22, 2026)
5.3.4 (Oct 24, 2026)
License
Source-availableFSL-1.1-Apache-2.0 (backend); Apache-2.0 client
Open source (permissive)Apache License 2.0 (core); Elastic License 2.0 (Harper Pro)
Free tier
✓
✓
popularity
WhichDB Score
26.0
9.1
Rank
#114
#317
GitHub stars
12.8K
90
Stack Overflow questions
–
–
scale & guarantees
Comfortable data size
Medium (≤ 10 TB)
Medium (≤ 10 TB)
Horizontal scaling
None
Addon
Multi-region
None
Active active
ACID
Full
Limited
Consistency
Strong
Eventual, Strong
Schema
Flexible
Flexible
Architecture
Serverless, Client server
Client server, Distributed, In memory
deployment
Self-hosted
✓
✓
Vendor-managed cloud
✓
✓
Serverless
✓
—
Embedded
—
—
Edge
—
✓
Clouds
–
–
capabilities
Transactions
✓
✓
Joins
—
✓
Secondary indexes
✓
✓
Full-text search
✓
—
Vector search
✓
✓
Geospatial
—
—
JSON
✓
✓
Change data capture
✓
—
Triggers
—
—
Stored procedures
✓
—
Materialized views
—
—
TTL / expiry
—
✓
Pub/Sub
✓
✓
Columnar storage
—
—
In-memory
—
✓
Durable persistence
✓
✓
Compression
—
—
Encryption at rest
—
—
Role-based access
—
✓
Time travel
—
—
Branching
—
—
Online schema changes
—
—
Streaming ingest
—
—
Offline sync
—
—
Runs in WebAssembly
—
—
interfaces
Query languages
TypeScript query functions
REST query parameters, GraphQL, SQL (limited)
Client languages
TypeScript, Python, Rust, Swift, Kotlin
JavaScript
Best for
OLTP, Vector search, RAG, Search
Cache, Edge, Pub/Sub, OLTP
Add more to this comparisonNot sure either fits? Try smart match

Convex vs Harper (formerly HarperDB): FAQ

What is the difference between Convex and Harper (formerly HarperDB)?

Convex: Reactive TypeScript backend with a transactional document database, server functions and live queries. Harper (formerly HarperDB): Node.js runtime that fuses database, cache, app logic and MQTT/WebSocket messaging in one process. Licensing: Convex is source-available (FSL-1.1-Apache-2.0 (backend); Apache-2.0 client); Harper (formerly HarperDB) is open source (permissive) (Apache License 2.0 (core); Elastic License 2.0 (Harper Pro)). Horizontal scaling is none in Convex and addon in Harper (formerly HarperDB). Transactions: Convex offers full ACID; Harper (formerly HarperDB) offers limited.

When should I choose Convex over Harper (formerly HarperDB)?

Choose Convex for realtime collaborative SaaS apps; AI chat and agent apps with vector search; and startups replacing a hand-built API plus cache. Choose Harper (formerly HarperDB) for edge caching and API acceleration in front of slower origins; real-time apps needing MQTT or WebSocket fan-out; and geo-distributed application backends.

Is Convex or Harper (formerly HarperDB) more popular?

Convex ranks #114 on the WhichDB Score (26.0/100) and Harper (formerly HarperDB) ranks #317 (9.1/100). Popularity is not fit: check the requirements that matter for your project.

Are Convex and Harper (formerly HarperDB) open source?

Not in the OSI sense. Convex is source-available: you can read the code, but the license restricts some uses, typically offering it as a competing managed service. License: FSL-1.1-Apache-2.0 (backend); Apache-2.0 client. Yes. Harper (formerly HarperDB) is open source. License: Apache License 2.0 (core); Elastic License 2.0 (Harper Pro).