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AxonOps Schema Registry

github.com

Free plan Open source LinuxAPISelf-hosted
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Spec score 8.6 #2 of 26 in Schema Registry Software

What it is

AxonOps Schema Registry is a free, Apache 2.0-licensed service for managing Apache Kafka schemas as an API-compatible replacement for Confluent Schema Registry. It handles Avro, Protobuf, and JSON Schema, including references and seven compatibility modes. Schemas can be stored in PostgreSQL, MySQL, or Cassandra, without requiring Kafka as the storage backend. The project says existing Confluent serializers and Java, Go, and Python Kafka clients can connect by changing the registry URL. Security options include Basic Auth, API keys, JWT, LDAP/AD, OIDC, mTLS, four RBAC roles, rate limiting, and TLS certificate auto-reload. Audit events can go to stdout, files, syslog, or webhooks. Client-side field encryption supports DEK/KEK registries and HashiCorp Vault or OpenBao Transit. Data contracts add metadata and rules. A beta MCP server supports several AI clients. It runs self-hosted on Linux, as a Docker container, or from source.

Spec sheet

What it does
AxonOps Schema Registry is a Kafka schema registry designed as a drop-in replacement for Confluent Schema Registry.Read 15 Oct 2026 · github.com
Purpose
AxonOps Schema Registry is an API-compatible replacement for Confluent Schema Registry for managing schemas used with Apache Kafka.Read 30 Sep 2026 · github.com
Deployment
The registry is a single statically linked binary of about 50 MB and can run as a Docker container or be built from source.Read 30 Sep 2026 · github.com
Security
Built-in security includes Basic Auth, API keys, JWT, LDAP/AD, OIDC, mTLS, four RBAC roles, rate limiting, and TLS certificate auto-reload.Read 30 Sep 2026 · github.com
Support
The project README says commercial support plans are offered by AxonOps; it also welcomes community issues and contributions.Read 30 Sep 2026 · github.com
Headquarters
London, United KingdomRead 23 Sep 2026 · github.com
Maker
The project identifies AxonOps as its maker and links to the AxonOps website.Read 30 Sep 2026 · github.com
AI integration
Its built-in MCP server is marked beta and supports AI clients including Claude, Cursor, VS Code Copilot, and Windsurf.Read 30 Sep 2026 · github.com
API compatibility
The registry implements the Confluent Schema Registry REST API v1, including enterprise endpoints.Read 15 Oct 2026 · github.com
API documentation
A built-in Swagger interface is available at the /docs endpoint.Read 15 Oct 2026 · github.com
Audit logging
Audit events can be sent to stdout, rotating files, syslog, and webhooks in JSON or CEF formats.Read 15 Oct 2026 · github.com
Authentication
Built-in authentication methods include Basic, API keys, JWT, LDAP/Active Directory, OIDC, and mutual TLS.Read 15 Oct 2026 · github.com
Business activities
Companies House lists software publishing and information-technology consultancy and service activities for AxonOps Limited.Read 15 Oct 2026 · find-and-update.company-information.service.gov.uk
Client compatibility
The maker says existing Confluent serializers and Java, Go, and Python Kafka clients work by pointing them at the registry URL.Read 30 Sep 2026 · github.com
Client libraries
Existing Confluent serializers for Java, Go, and Python can work by changing the registry URL.Read 15 Oct 2026 · github.com
Company founded
LinkedIn gives AxonOps a 2022 founding year.Read 15 Oct 2026 · uk.linkedin.com
Company headquarters
LinkedIn identifies AxonOps headquarters as London, United Kingdom.Read 15 Oct 2026 · uk.linkedin.com
Company size
LinkedIn lists AxonOps as having 11–50 employees and 13 discoverable employees.Read 15 Oct 2026 · uk.linkedin.com
Compatibility modes
The product supports seven compatibility modes, including backward, forward, full, and transitive variants.Read 15 Oct 2026 · github.com
Data contracts
Data contracts attach metadata tags and domain, migration, and encoding rules to schemas, with defaults and per-subject overrides.Read 30 Sep 2026 · github.com
Deployment footprint
The project describes a statically linked binary of about 50 MB with no runtime dependencies.Read 15 Oct 2026 · github.com
Developer prerequisites
The development guide lists Go 1.26 or newer and Docker, with Java 17+, Maven, and Python 3 optional for compatibility tests.Read 15 Oct 2026 · github.com
Documentation depth
Documentation covers installation, configuration, storage, schema types, compatibility, security, auditing, deployment, monitoring, migration, encryption, exporters, MCP, and troubleshooting.Read 15 Oct 2026 · github.com
Encryption
A DEK and KEK registry provides client-side field-level encryption compatible with Confluent serializers.Read 15 Oct 2026 · github.com
Field encryption
Client-side field encryption includes a DEK/KEK registry and production-ready integrations with HashiCorp Vault and OpenBao Transit.Read 30 Sep 2026 · github.com
High availability
Multiple stateless instances can run behind a load balancer using database-level locking with PostgreSQL or MySQL.Read 15 Oct 2026 · github.com
Kafka dependency
Kafka is not required for schema storage because the service uses external databases.Read 15 Oct 2026 · github.com
KMS integrations
Production KMS integrations include HashiCorp Vault and OpenBao Transit.Read 15 Oct 2026 · github.com
Latest release
Release v0.4.0-mcp-phase7 added MCP and enterprise audit features, Kubernetes environment-variable coverage, a MySQL deadlock retry, per-schema bulk-import audit events, and a Go upgrade prompted by security alerts.Read 15 Oct 2026 · github.com
Legal entity
UK Companies House identifies the maker as AXONOPS LIMITED, an active private limited company incorporated on 13 May 2022.Read 15 Oct 2026 · find-and-update.company-information.service.gov.uk
Licence
The repository is released under the Apache License 2.0.Read 15 Oct 2026 · github.com
Limit: exporter replication
The exporter API stores replication definitions, but active cross-registry replication requires an external agent.Read 15 Oct 2026 · github.com
Limit: KMS coverage
AWS KMS, Azure Key Vault, and Google Cloud KMS support is described as forthcoming.Read 15 Oct 2026 · github.com
Limit: MCP maturity
The MCP server is marked beta and its APIs, tool names, and configuration may change before version 1.0.Read 15 Oct 2026 · github.com
MCP integration
A built-in Model Context Protocol server connects schema workflows to clients such as Claude, Cursor, VS Code Copilot, and Windsurf.Read 15 Oct 2026 · github.com
MCP scale
The MCP server advertises 107 tools, 47 resources, and 33 guided prompts.Read 15 Oct 2026 · github.com
Notable limit
The Cassandra storage backend requires Cassandra 5.0 or later; earlier versions are unsupported.Read 30 Sep 2026 · github.com
Observability
The service exposes 19 Prometheus metrics and a health endpoint for load balancers and Kubernetes probes.Read 15 Oct 2026 · github.com
Praise: lightweight open source
A Reddit commenter described the project as Apache 2.0 licensed, written in Go, enterprise-security oriented, and lightweight compared with Java registries.Read 15 Oct 2026 · reddit.com
RBAC
The service includes role-based access control with four roles.Read 15 Oct 2026 · github.com
Registered office
The registered office is 124 City Road, London, England, EC1V 2NX.Read 15 Oct 2026 · find-and-update.company-information.service.gov.uk
Schema analysis
Additional analysis APIs provide field and type search, similarity detection, quality scoring, complexity grading, and migration planning.Read 15 Oct 2026 · github.com
Schema formats
It supports Avro, Protocol Buffers, and JSON Schema.Read 15 Oct 2026 · github.com
Schema governance
Data contracts can attach metadata, domain rules, migration rules, and encoding rules to schemas.Read 15 Oct 2026 · github.com
Schema references
Cross-subject schema references are supported for the three schema formats.Read 15 Oct 2026 · github.com
Storage
It can store schemas in PostgreSQL, MySQL, or Cassandra and does not require Kafka as its storage backend.Read 30 Sep 2026 · github.com
Storage backends
Schemas can be stored in PostgreSQL, MySQL, Cassandra, or in-memory storage.Read 15 Oct 2026 · github.com

Plans and prices

AxonOps Schema Registry Free 100% free and open source; Apache 2.0 licensed No hidden costs · no premium tiers · no license keys Read 30 Sep 2026 · github.com
Free Free forever all features · no premium tiers · no license keys Read 15 Oct 2026 · github.com

Every AxonOps Schema Registry plan and price →

Strong points and limits

Strong points

  • Free Apache 2.0-licensed plan
  • Supports Avro, Protobuf, and JSON Schema
  • Multiple database storage backends
  • Broad authentication and authorization options
  • Runs as a small Docker or source-built binary

Limits

  • Cassandra storage requires Cassandra 5.0 or later
  • Built-in MCP server is marked beta
  • Commercial support is offered separately

Who it suits

It suits Kafka teams wanting self-hosted schema management with multiple storage, security, audit, and encryption options. Existing Confluent-client users can connect through the registry URL.

Verdict

AxonOps Schema Registry provides broad schema, security, and deployment controls without a license fee. Teams using older Cassandra versions or depending on production-ready MCP support should account for the stated limits.

Where Specifiction places it

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