Open-Source Databases · scalar-labs

scalardb

ScalarDB is a Java-based HTAP (Hybrid Transactional/Analytical Processing) engine that adds ACID transactions and real-time analytics on top of diverse backend databases like PostgreSQL, MySQL, DynamoDB, Cassandra, and Azure Cosmos DB. It simplifies multi-database architectures by providing a unified transaction layer without requiring database replacement.

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Source: GitHub — github.com/scalar-labs/scalardb

640

GitHub stars

Forks

Java

Primary language

Apache-2.0

License (OSI-approved)

Key facts

Objective fields from the source. Values we can't verify are shown as “Unknown” rather than guessed.

Field	Value
Repository	scalar-labs/scalardb
Owner	scalar-labs
Primary language	Java
License	Apache-2.0 — OSI-approved
Stars	640
Forks	44
Open issues	22
Latest release	v3.18.0 (2026-05-01)
Last updated	2026-07-07
Source	https://github.com/scalar-labs/scalardb

What scalardb is

ScalarDB is a distributed transaction coordinator written in Java that abstracts multiple heterogeneous databases through a common API, supporting ACID guarantees and cross-database transactions. The project offers both open-source Core and commercial Cluster editions, with support for SQL APIs and vector search in enterprise variants.

Quickstart

Get the scalardb source

Clone the repository and explore it locally.

terminalbash

1git clone https://github.com/scalar-labs/scalardb.git2cd scalardb3# follow the project's README for install & configuration

Need it deployed, integrated, or customized instead? DEV.co ships production installs.

Best use cases

Multi-database ACID transactions

When business logic requires ACID guarantees across data stored in different database systems (e.g., transactions spanning PostgreSQL and DynamoDB), ScalarDB provides a unified transaction layer without application refactoring.

Legacy database modernization

Organizations with established databases (Oracle, MySQL, Cassandra) that need to adopt cloud-native databases or transition to NoSQL can use ScalarDB as a compatibility layer to preserve transaction semantics during migration.

Real-time analytics with transactional consistency

Microservice architectures requiring consistent analytical views of transactional data across multiple backend databases can leverage ScalarDB's HTAP capabilities to avoid eventual consistency issues in reporting.

Implementation considerations

Java library integration: ScalarDB is consumed as a Maven/Gradle dependency; ensure Java application compatibility and version alignment with v3.18.0.
Backend database provisioning: Requires pre-existing databases (PostgreSQL, MySQL, DynamoDB, etc.); ScalarDB does not manage underlying database lifecycle.
Configuration management: Review both Core and Cluster configuration documentation; enterprise Cluster features (auth/ABAC/vector search) are licensed separately.
Schema and data model design: Transactional semantics across heterogeneous stores require careful schema normalization; distributed transaction overhead increases with data size and cross-database joins.
Testing and validation: Multi-database ACID correctness is complex; plan for thorough integration and chaos testing to verify transaction guarantees.

When to avoid it — and what to weigh

Greenfield projects with single-database fit — If your application naturally fits a single database technology and scale, adding ScalarDB introduces unnecessary abstraction overhead and operational complexity.
Real-time, ultra-low-latency requirements — ScalarDB's coordination layer adds latency compared to direct database access. Systems requiring sub-millisecond response times or strict hard-real-time guarantees should evaluate carefully.
Limited Java ecosystem or polyglot-first architecture — ScalarDB is Java-primary; non-Java services require client libraries or network calls. If you are building heterogeneous language systems without strong Java presence, integration cost rises significantly.
Minimal DevOps or infrastructure expertise — Distributed transaction coordination adds operational surface area. Teams without experience managing distributed systems may face steep debugging and troubleshooting curves.

License & commercial use

ScalarDB Core is released under Apache License 2.0 (Apache-2.0), a permissive OSI-approved license allowing commercial use, modification, and distribution with minimal restrictions.

Apache-2.0 permits commercial use, but ScalarDB has two editions: open-source Core and commercial Cluster. Commercial use of Core is permissible under Apache-2.0. However, enterprise features (authentication, ABAC, vector search) are restricted to the paid Cluster edition. Verify Cluster licensing terms with Scalar Labs before production deployment.

DEV.co evaluation signals

Editorial assessment — not user reviews. Directional, with an explicit confidence level.

Signal	Assessment
Maintenance	Active
Documentation	Strong
License clarity	Clear
Deployment complexity	High
DEV.co fit	Good
Assessment confidence	High

Security considerations

ScalarDB Cluster (enterprise) offers user authentication/authorization and attribute-based access control (ABAC); these are not available in open-source Core. No details provided on encryption in transit/at rest, vulnerability disclosure process, or security audit history. Integration with underlying database security models is architecture-dependent. Distributed transaction logs and state management introduce new attack surface; requires threat modeling for your deployment. Security posture should be verified through official security documentation and, if applicable, independent audit before production use.

Alternatives to consider

Distributed saga orchestration (Axon Framework, Temporal)

Saga patterns provide eventual consistency and cross-service transactions without requiring a transaction coordinator layer. Simpler operational model but weaker consistency guarantees than ACID.

Database-native sharding (Vitess, Citus)

Scales single database technology horizontally while preserving ACID. Requires homogeneous database choice and is less flexible for multi-database architectures but simpler operationally.

Event sourcing + CQRS

Builds consistency through immutable event logs and eventual consistency patterns. Decouples transaction and query models but adds complexity in reconciliation and requires careful event schema design.

Software development agency

Build on scalardb with DEV.co software developers

Review the official documentation at scalardb.scalar-labs.com, evaluate Core vs. Cluster licensing needs, and run a Quickstart sample with your target databases. Contact Scalar Labs for Cluster pricing and enterprise feature details.

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scalardb FAQ

Does ScalarDB replace my databases?

No. ScalarDB is a coordination layer that sits on top of existing databases (PostgreSQL, MySQL, DynamoDB, etc.). It does not replace them; it provides ACID semantics across them.

What is the difference between ScalarDB Core and ScalarDB Cluster?

Core is open-source Apache-2.0 and embedded as a library; Cluster is commercial and runs as a separate service. Cluster adds authentication/authorization, ABAC, and vector search. Specific Cluster licensing and cost are not detailed in the provided data.

Does ScalarDB add significant latency?

ScalarDB adds coordination overhead compared to direct database access. Impact depends on transaction complexity, database latency, and network. For latency-sensitive systems, benchmark with your specific workload.

Can I use ScalarDB from languages other than Java?

Core is Java-primary. ScalarDB Cluster documentation mentions client APIs; specifics for non-Java languages (REST, gRPC, etc.) are not clearly stated in the provided README excerpt.

Work with a software development agency

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