whichdb
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Harper (formerly HarperDB) vs Redis

Harper (formerly HarperDB): Node.js runtime that fuses database, cache, app logic and MQTT/WebSocket messaging in one process. Redis: The in-memory data structure server that became the default cache, now with search, JSON and vectors built in.

key differences

  • Harper (formerly HarperDB) is primarily a document database; Redis is key-value.
  • Licensing: Harper (formerly HarperDB) is open source (permissive) (Apache License 2.0 (core); Elastic License 2.0 (Harper Pro)); Redis is open source (copyleft) (Tri-license: AGPLv3, RSALv2 or SSPLv1 (Redis 8+)).
  • Horizontal scaling is addon in Harper (formerly HarperDB) and native in Redis.
  • Only Harper (formerly HarperDB) has joins.
  • Only Redis has full-text search, geospatial, stored procedures, streaming ingest.

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

choose redis for

  • +Application and database query caching
  • +Session storage and user tokens
  • +Rate limiting and distributed locks
  • +Leaderboards and counters

best at · Cache, Sessions, Queue

Harper (formerly HarperDB)Node.js runtime that fuses database, cache, app logic and MQTT/WebSocket messaging in one process.
RedisThe in-memory data structure server that became the default cache, now with search, JSON and vectors built in.
overview
Primary model
Document
Key-Value
Also supports
Key-Value, Vector
Document, Vector, Time-Series, Search Engine
Type
Backend platform
Database engine
Status
Active
Active
Developer
HarperDB, Inc.
Redis Ltd.
First release
2017
2009
Latest version
5.3.4 (Oct 24, 2026)
8.10.3 (Oct 26, 2026)
License
Open source (permissive)Apache License 2.0 (core); Elastic License 2.0 (Harper Pro)
Open source (copyleft)Tri-license: AGPLv3, RSALv2 or SSPLv1 (Redis 8+)
Free tier
✓
✓
popularity
WhichDB Score
9.1
84.3
Rank
#317
#2
GitHub stars
90
77.1K
Stack Overflow questions
–
25.4K
scale & guarantees
Comfortable data size
Medium (≤ 10 TB)
Medium (≤ 10 TB)
Horizontal scaling
Addon
Native
Multi-region
Active active
Active active
ACID
Limited
Limited
Consistency
Eventual, Strong
Eventual
Schema
Flexible
Schemaless
Architecture
Client server, Distributed, In memory
In memory, Single node, Primary replica, Distributed, Client server
deployment
Self-hosted
✓
✓
Vendor-managed cloud
✓
✓
Serverless
—
—
Embedded
—
—
Edge
✓
—
Clouds
–
AWS, Google Cloud, Azure, DigitalOcean, Heroku, Render
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
REST query parameters, GraphQL, SQL (limited)
Redis commands (RESP), Lua, Redis Query Engine (FT.*)
Client languages
JavaScript
Python, Java, JavaScript, Go, C#, Rust, Ruby, PHP
Best for
Cache, Edge, Pub/Sub, OLTP
Cache, Sessions, Queue, Pub/Sub
Add more to this comparisonNot sure either fits? Try smart match

Harper (formerly HarperDB) vs Redis: FAQ

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

Harper (formerly HarperDB): Node.js runtime that fuses database, cache, app logic and MQTT/WebSocket messaging in one process. Redis: The in-memory data structure server that became the default cache, now with search, JSON and vectors built in. Harper (formerly HarperDB) is primarily a document database; Redis is key-value. Licensing: Harper (formerly HarperDB) is open source (permissive) (Apache License 2.0 (core); Elastic License 2.0 (Harper Pro)); Redis is open source (copyleft) (Tri-license: AGPLv3, RSALv2 or SSPLv1 (Redis 8+)). Horizontal scaling is addon in Harper (formerly HarperDB) and native in Redis.

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

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. Choose Redis for application and database query caching; session storage and user tokens; and rate limiting and distributed locks.

Is Harper (formerly HarperDB) or Redis more popular?

Redis ranks #2 on the WhichDB Score (84.3/100) and Harper (formerly HarperDB) ranks #317 (9.1/100). Popularity is not fit: check the requirements that matter for your project.

Are Harper (formerly HarperDB) and Redis open source?

Yes. Harper (formerly HarperDB) is open source. License: Apache License 2.0 (core); Elastic License 2.0 (Harper Pro). Yes. Redis is open source. License: Tri-license: AGPLv3, RSALv2 or SSPLv1 (Redis 8+).