Polyglot DB MCP

One MCP server. 20 databases. Zero context switching.

Query PostgreSQL, MongoDB, Neo4j, Elasticsearch, Redis, and 15 more databases through a single unified interface. Built with ReScript, runs on Deno.

Table of Contents

Why Polyglot DB?

Modern applications use multiple databases — SQL for transactions, Redis for caching, Elasticsearch for search, vectors for AI. Switching between CLIs, APIs, and query languages is exhausting.

Polyglot DB MCP gives Claude (and other MCP clients) direct access to all your databases through natural language:

Find all users in PostgreSQL who signed up last week, then check if they’re in the Redis cache

Search Elasticsearch for 'authentication errors' and correlate with the MongoDB audit log

Store this embedding in Qdrant and link it to the Neo4j knowledge graph

Installation

Option A: Direct (Recommended for development)

# Clone the repository
git clone https://github.com/hyperpolymath/polyglot-db-mcp.git
cd polyglot-db-mcp

# Add to Claude Code
claude mcp add polyglot-db -- deno run \
  --allow-net --allow-read --allow-write --allow-env \
  $(pwd)/index.js

Option B: Container (Recommended for production)

# Using nerdctl (containerd)
nerdctl run -d --name polyglot-db \
  -e POSTGRES_HOST=host.docker.internal \
  -e MONGODB_URL=mongodb://host.docker.internal:27017 \
  ghcr.io/hyperpolymath/polyglot-db-mcp:latest

# Using podman
podman run -d --name polyglot-db \
  -e POSTGRES_HOST=host.containers.internal \
  ghcr.io/hyperpolymath/polyglot-db-mcp:latest

# Using docker
docker run -d --name polyglot-db \
  -e POSTGRES_HOST=host.docker.internal \
  ghcr.io/hyperpolymath/polyglot-db-mcp:latest

Option C: Deno Deploy (Serverless)

deployctl deploy --project=polyglot-db index.js

Quick Start

1. Configure your databases

Create a .env file or export environment variables:

# Example: PostgreSQL + Redis + Elasticsearch
export POSTGRES_HOST=localhost POSTGRES_DATABASE=myapp
export DRAGONFLY_HOST=localhost
export ELASTICSEARCH_URL=http://localhost:9200

2. Ask Claude

"What databases are connected?"
"Show me the schema of the users table in PostgreSQL"
"Cache this result in Redis with a 1 hour TTL"

Supported Databases

Relational

Database	License	Best For	Tools
PostgreSQL	PostgreSQL (FOSS)	Complex queries, ACID, extensions (PostGIS, pgvector)	`pg_*`
MariaDB	GPL v2 (FOSS)	Web apps, MySQL compatibility	`maria_*`
SQLite	Public Domain	Local storage, embedded, single-file	`sqlite_*`

Document

Database	License	Best For	Tools
MongoDB	SSPL	Flexible schemas, horizontal scaling	`mongo_*`
SurrealDB	BSL/Apache 2.0	Multi-model (doc + graph + SQL)	`surreal_*`
ArangoDB	Apache 2.0 (FOSS)	Multi-model (doc + graph + KV), AQL	`arango_*`
CouchDB	Apache 2.0 (FOSS)	Document DB with HTTP API, Mango queries	`couchdb_*`

Wide Column

Database	License	Best For	Tools
Cassandra	Apache 2.0 (FOSS)	Distributed, high availability, time-series	`cassandra_*`

Graph

Database	License	Best For	Tools
Neo4j	GPL v3 / Commercial	Relationships, social networks, fraud detection	`neo4j_*`
Virtuoso	GPL v2 / Commercial	RDF triplestore, SPARQL, linked data	`virtuoso_*`

Cache & Key-Value

Database	License	Best For	Tools
Dragonfly	BSL	Redis replacement, 25x faster	`dragonfly_*`
Memcached	BSD (FOSS)	Simple distributed caching	`memcached_*`
LMDB	OpenLDAP (FOSS)	Embedded KV with ACID	`lmdb_*`

Search

Database	License	Best For	Tools
Elasticsearch	Elastic License 2.0	Full-text search, log analytics	`es_*`
Meilisearch	MIT (FOSS)	Instant, typo-tolerant search	`meili_*`

Vector

Database	License	Best For	Tools
Qdrant	Apache 2.0 (FOSS)	AI embeddings, semantic search	`qdrant_*`

Time Series

Database	License	Best For	Tools
InfluxDB	MIT (v1)	IoT, monitoring, metrics	`influx_*`

Analytics

Database	License	Best For	Tools
DuckDB	MIT (FOSS)	OLAP, query CSV/Parquet/JSON directly	`duck_*`

Specialized

Database	License	Best For	Tools
XTDB	MIT (FOSS)	Bitemporal queries, audit trails	`xtdb_*`
iTop	AGPL v3 (FOSS)	IT asset management, CMDB	`itop_*`

Note	FOSS = Free & Open Source \| Source-Available = viewable but restricted

Configuration

Each database reads from environment variables. Only configure what you need.

PostgreSQL

POSTGRES_HOST=localhost
POSTGRES_PORT=5432
POSTGRES_DATABASE=mydb
POSTGRES_USER=postgres
POSTGRES_PASSWORD=secret

# Connection pool (optional)
POSTGRES_POOL_MAX=10         # Max connections
POSTGRES_IDLE_TIMEOUT=30     # Seconds before idle connection closed
POSTGRES_CONNECT_TIMEOUT=10  # Connection timeout in seconds

MongoDB

MONGODB_URL=mongodb://localhost:27017
MONGODB_DATABASE=mydb

# Connection pool (optional)
MONGODB_POOL_MAX=10           # Max connections
MONGODB_POOL_MIN=1            # Min connections
MONGODB_IDLE_TIMEOUT=30000    # Idle timeout in ms
MONGODB_CONNECT_TIMEOUT=10000 # Connect timeout in ms
MONGODB_SERVER_TIMEOUT=30000  # Server selection timeout in ms

Neo4j

NEO4J_URL=bolt://localhost:7687
NEO4J_USERNAME=neo4j
NEO4J_PASSWORD=secret

Elasticsearch

ELASTICSEARCH_URL=http://localhost:9200
ELASTICSEARCH_USERNAME=elastic    # optional
ELASTICSEARCH_PASSWORD=secret     # optional

Dragonfly / Redis

DRAGONFLY_HOST=localhost
DRAGONFLY_PORT=6379
DRAGONFLY_PASSWORD=             # optional

InfluxDB

INFLUXDB_URL=http://localhost:8086
INFLUXDB_TOKEN=your-token
INFLUXDB_ORG=your-org
INFLUXDB_BUCKET=your-bucket

SurrealDB

SURREAL_URL=http://localhost:8000
SURREAL_NAMESPACE=test
SURREAL_DATABASE=test
SURREAL_USERNAME=root
SURREAL_PASSWORD=root

ArangoDB

ARANGO_URL=http://localhost:8529
ARANGO_DATABASE=_system
ARANGO_USERNAME=root
ARANGO_PASSWORD=

Virtuoso

VIRTUOSO_ENDPOINT=http://localhost:8890/sparql
VIRTUOSO_UPDATE_ENDPOINT=http://localhost:8890/sparql-auth
VIRTUOSO_USERNAME=
VIRTUOSO_PASSWORD=
VIRTUOSO_DEFAULT_GRAPH=

CouchDB

COUCHDB_URL=http://localhost:5984
COUCHDB_USERNAME=admin
COUCHDB_PASSWORD=secret
COUCHDB_DATABASE=mydb

Cassandra

CASSANDRA_CONTACT_POINTS=localhost    # comma-separated list
CASSANDRA_DATACENTER=datacenter1
CASSANDRA_KEYSPACE=mykeyspace
CASSANDRA_USERNAME=cassandra
CASSANDRA_PASSWORD=cassandra

SQLite

SQLITE_PATH=./data.db     # or :memory:

DuckDB

DUCKDB_PATH=./analytics.db  # or :memory:

Qdrant

QDRANT_URL=http://localhost:6333
QDRANT_API_KEY=               # optional

Meilisearch

MEILISEARCH_URL=http://localhost:7700
MEILISEARCH_API_KEY=          # optional

MariaDB

MARIADB_HOST=localhost
MARIADB_PORT=3306
MARIADB_USER=root
MARIADB_PASSWORD=secret
MARIADB_DATABASE=mydb

# Connection pool (optional)
MARIADB_POOL_MAX=10            # Max connections
MARIADB_ACQUIRE_TIMEOUT=10000  # Acquire timeout in ms
MARIADB_IDLE_TIMEOUT=30000     # Idle timeout in ms
MARIADB_CONNECT_TIMEOUT=10000  # Connect timeout in ms

Memcached

MEMCACHED_SERVERS=localhost:11211

LMDB

LMDB_PATH=./lmdb-data

XTDB

XTDB_URL=http://localhost:3000

iTop

ITOP_URL=http://localhost/itop
ITOP_USERNAME=admin
ITOP_PASSWORD=secret

Usage Examples

Meta Tools

db_list              List all 18 supported databases
db_status            Check which databases are currently connected
db_help [database]   Get available tools for a specific database

Natural Language Queries

Ask Claude things like:

PostgreSQL:

Create a users table with id, email, and created_at columns

Find all orders over $100 from the last month

MongoDB:

Insert a new document into the products collection

Aggregate sales by category with a $match and $group pipeline

Neo4j:

Find the shortest path between User:alice and User:bob

Show all nodes connected to the 'Engineering' department

Elasticsearch:

Search for documents containing 'critical error' in the logs index

Get the mapping for the products index

Redis/Dragonfly:

Set user:123:session with a 30 minute TTL

Get all keys matching cache:*

Qdrant:

Search for vectors similar to this embedding in the documents collection

Create a new collection with 1536 dimensions for OpenAI embeddings

Cross-Database:

Query users from PostgreSQL and cache the result in Redis

Find products in MongoDB and index them in Meilisearch

Architecture

polyglot-db-mcp/
├── index.js                    # MCP server entry point
├── src/                        # ReScript source (core adapters)
│   ├── Adapter.res             # Shared types
│   ├── bindings/               # Database client FFI
│   └── adapters/               # PostgreSQL, MongoDB, SQLite, Dragonfly, Elasticsearch
├── adapters/                   # JavaScript adapters (exotic databases)
├── lib/es6/                    # Compiled ReScript output
└── STATE.scm                   # Project state tracking

Language Policy

Component	Language	Rationale
Core adapters (5)	ReScript	Type safety, smaller bundles
Exotic adapters (11)	JavaScript	Pragmatic for v1.x
Future (v2.0.0)	100% ReScript	RSR Gold compliance

Important

TypeScript is prohibited. We chose ReScript for its superior type inference and ML heritage.

Development

Building ReScript

npm install           # Install ReScript compiler
npm run res:build     # Compile to JavaScript
npm run res:watch     # Watch mode

Running Locally

deno task start
# or
deno run --allow-net --allow-read --allow-write --allow-env index.js

Git Hooks

Enable the pre-commit hook to enforce language policy:

git config core.hooksPath .githooks

Adding a New Database

Create src/adapters/YourDb.res:

// SPDX-License-Identifier: MIT
open Adapter

let name = "yourdb"
let description = "Your database description"

let connect = async () => { /* ... */ }
let disconnect = async () => { /* ... */ }
let isConnected = async () => { /* ... */ }

let tools: Js.Dict.t<toolDefAny> = {
  let dict = Js.Dict.empty()
  Js.Dict.set(dict, "yourdb_query", {
    description: "Execute a query",
    params: makeParams([("query", stringParam("Query to run"))]),
    handler: queryHandler,
  })
  dict
}

Then import in index.js and rebuild.

Roadmap

Version	Status	Highlights
1.0.0	Released	16 databases, ReScript core, CI/CD
1.1.0	In Progress	Connection pooling, container images, better errors
1.2.0	Planned	Cross-database pipelines, caching helpers
2.0.0	Vision	100% ReScript, RSR Gold compliance

arango-mcp — ArangoDB MCP server
virtuoso-mcp — Virtuoso SPARQL MCP server

License

Dual-licensed: MIT OR AGPL-3.0-or-later — your choice.

We encourage (but don’t require) layering the Palimpsest License for ethical AI development practices.

Name		Name	Last commit message	Last commit date
Latest commit History 29 Commits
.claude		.claude
.githooks		.githooks
.github		.github
.well-known		.well-known
adapters		adapters
src		src
.gitattributes		.gitattributes
.gitignore		.gitignore
.tool-versions		.tool-versions
AI.scm		AI.scm
CHANGELOG.md		CHANGELOG.md
CLAUDE.md		CLAUDE.md
CODE_OF_CONDUCT.adoc		CODE_OF_CONDUCT.adoc
CONTRIBUTING.adoc		CONTRIBUTING.adoc
Containerfile		Containerfile
ECOSYSTEM.scm		ECOSYSTEM.scm
FUNDING.yml		FUNDING.yml
GOVERNANCE.adoc		GOVERNANCE.adoc
LICENSE.txt		LICENSE.txt
MAINTAINERS.adoc		MAINTAINERS.adoc
META.scm		META.scm
README.adoc		README.adoc
SECURITY.adoc		SECURITY.adoc
STATE.scm		STATE.scm
SYNDICATION.adoc		SYNDICATION.adoc
TS_CONVERSION_NEEDED.md		TS_CONVERSION_NEEDED.md
deno.json		deno.json
index.js		index.js
justfile		justfile
package-lock.json		package-lock.json
package.json		package.json
rescript.json		rescript.json
server.json		server.json
smithery.yaml		smithery.yaml

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License

hyperpolymath/poly-db-mcp

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Polyglot DB MCP

Why Polyglot DB?

Installation

Option A: Direct (Recommended for development)

Option B: Container (Recommended for production)

Option C: Deno Deploy (Serverless)

Quick Start

1. Configure your databases

2. Ask Claude

Supported Databases

Relational

Document

Wide Column

Graph

Cache & Key-Value

Search

Vector

Time Series

Analytics

Specialized

Configuration

PostgreSQL

MongoDB

Neo4j

Elasticsearch

Dragonfly / Redis

InfluxDB

SurrealDB

ArangoDB

Virtuoso

CouchDB

Cassandra

SQLite

DuckDB

Qdrant

Meilisearch

MariaDB

Memcached

LMDB

XTDB

iTop

Usage Examples

Meta Tools

Natural Language Queries

Architecture

Language Policy

Development

Building ReScript

Running Locally

Git Hooks

Adding a New Database

Roadmap

Related Projects

License

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