Johnny

A lightweight, project-agnostic semantic memory system for storing and retrieving text with vector embeddings.

Johnny provides the retrieval layer for RAG (Retrieval-Augmented Generation) applications. Store facts, conversations, or documents with auto-generated embeddings, then query by semantic similarity.

Features

• Vector embeddings via OpenAI's text-embedding-3-small (1536 dimensions)
• PostgreSQL + pgvector for storage and similarity search
• Namespace isolation - separate memory spaces per user, project, or context
• Flexible filtering - by type, tags, importance, recency
• Usage tracking - mention counts and cooldowns to avoid repetition
• TTL expiration - automatic cleanup of stale memories
• Prisma integration - works with your existing Prisma client

Installation

npm install @ticktockbent/johnny

Peer Dependencies

Johnny requires these packages in your project:

npm install @prisma/client

Johnny is compatible with Prisma versions 5 and 7. Install the version that matches your project:

npm install @prisma/client@^5.0.0  # Prisma 5.x (fully tested)
npm install @prisma/client@^7.0.0  # Prisma 7.x (fully tested)

Note: Prisma 6.x support is untested and may have compatibility issues. We recommend using Prisma 5.x or upgrading to 7.x.

Quick Start

1. Add the Memory model to your Prisma schema

// schema.prisma

generator client {
  provider        = "prisma-client-js"
  previewFeatures = ["postgresqlExtensions"]
}

datasource db {
  provider   = "postgresql"
  url        = env("DATABASE_URL")
  extensions = [vector]
}

model Memory {
  id              String    @id @default(cuid())
  namespace       String
  content         String    @db.Text
  embedding       Unsupported("vector(1536)")?
  type            String?
  tags            String[]  @default([])
  source          String?
  importance      Float?
  expiresAt       DateTime?
  lastMentionedAt DateTime?
  mentionCount    Int       @default(0)
  createdAt       DateTime  @default(now())
  updatedAt       DateTime  @updatedAt

  @@index([namespace])
  @@index([namespace, type])
  @@index([namespace, source])
  @@index([expiresAt])
}

2. Set up the database

# Push schema to database
npx prisma db push

# Create the vector similarity index (run via psql or database console)
psql $DATABASE_URL -c "CREATE INDEX memory_embedding_idx ON \"Memory\" USING ivfflat (embedding vector_cosine_ops) WITH (lists = 100);"

3. Initialize and use

import { PrismaClient } from '@prisma/client'
import { MemoryService } from '@ticktockbent/johnny'

const prisma = new PrismaClient()

const memory = new MemoryService({
  prisma,
  embeddingApiKey: process.env.OPENAI_API_KEY!,
  defaultNamespace: 'my-app',
})

// Store a memory
await memory.store('user:123', 'User loves hiking in the mountains', {
  type: 'preference',
  tags: ['hobby', 'outdoors'],
  importance: 0.8,
})

// Search by semantic similarity
const results = await memory.search('user:123', 'outdoor activities', {
  limit: 5,
  maxDistance: 0.7,
})

// Results include distance scores (lower = more similar)
console.log(results[0].content)   // "User loves hiking in the mountains"
console.log(results[0].distance)  // 0.42

API Reference

MemoryService

Constructor

new MemoryService({
  prisma: PrismaClient,           // Your Prisma client instance
  embeddingApiKey: string,        // OpenAI API key
  embeddingModel?: string,        // Default: 'text-embedding-3-small'
  defaultNamespace?: string,      // Optional default namespace
})

Methods

store(namespace, content, metadata?)

Store a new memory with auto-generated embedding.

const memory = await memory.store('user:123', 'Content to remember', {
  type: 'fact',              // App-defined category
  tags: ['tag1', 'tag2'],    // Flexible labels for filtering
  source: 'conversation:456', // Origin reference
  importance: 0.8,           // Ranking signal (0-1)
  expiresAt: new Date(),     // Auto-delete after this time
})

storeMany(namespace, items[])

Batch store multiple memories (more efficient for bulk operations).

const memories = await memory.storeMany('user:123', [
  { content: 'First fact', metadata: { type: 'fact' } },
  { content: 'Second fact', metadata: { type: 'fact' } },
])

search(namespace, query, options?)

Find memories semantically similar to a query.

const results = await memory.search('user:123', 'search query', {
  limit: 10,                    // Max results (default: 10)
  maxDistance: 0.5,             // Similarity threshold (default: 0.5, lower = stricter)
  types: ['fact', 'preference'], // Filter by type
  tags: ['important'],          // Must have ALL these tags
  minImportance: 0.5,           // Minimum importance score
  excludeMentionedWithin: 24,   // Exclude if mentioned within N hours
})

// Returns MemorySearchResult[]
// { id, content, type, tags, source, importance, distance, createdAt, lastMentionedAt, mentionCount }

get(id)

Retrieve a specific memory by ID.

const memory = await memory.get('memory-id')

update(id, updates)

Update a memory's metadata (does not re-embed content).

const updated = await memory.update('memory-id', {
  type: 'new-type',
  tags: ['new', 'tags'],
  importance: 0.9,
  expiresAt: null,  // Remove expiration
})

delete(id)

Delete a specific memory.

await memory.delete('memory-id')

recordMention(id)

Track that a memory was used. Updates lastMentionedAt and increments mentionCount.

await memory.recordMention('memory-id')

deleteByNamespace(namespace)

Delete all memories in a namespace.

const count = await memory.deleteByNamespace('user:123')

deleteBySource(namespace, source)

Delete all memories from a specific source.

const count = await memory.deleteBySource('user:123', 'document:456')

pruneExpired()

Delete all memories past their expiresAt timestamp.

const count = await memory.pruneExpired()

getStats(namespace)

Get statistics for a namespace.

const stats = await memory.getStats('user:123')
// { totalMemories, byType, oldestMemory, newestMemory, expiringWithin7Days }

Testing

Johnny includes a MockMemoryService for unit testing without a database or API calls:

import { MockMemoryService } from '@ticktockbent/johnny'
// or
import { MockMemoryService } from '@ticktockbent/johnny/testing'

const memory = new MockMemoryService({
  defaultNamespace: 'test',
})

// Same API as MemoryService
await memory.store(undefined, 'Test content')
const results = await memory.search(undefined, 'test')

// Reset between tests
memory.clear()

The mock uses deterministic hash-based embeddings and cosine similarity, so search results are consistent but not semantically meaningful.

Error Handling

Johnny exports typed errors for specific failure cases:

import {
  MemoryError,           // Base error class
  EmbeddingError,        // OpenAI API failures
  NotFoundError,         // Memory not found
  NamespaceRequiredError, // Missing namespace
  DatabaseError,         // Database operation failures
} from '@ticktockbent/johnny'

try {
  await memory.update('nonexistent', { type: 'x' })
} catch (error) {
  if (error instanceof NotFoundError) {
    console.log(`Memory ${error.id} not found`)
  }
}

Deployment

Vercel + Vercel Postgres

Vercel Postgres (powered by Neon) supports pgvector:

1. Enable the extension in your database:

   CREATE EXTENSION IF NOT EXISTS vector;

2. Add the Memory model to your schema and push

3. Create the vector index via Vercel's SQL console

4. Use with your existing Prisma client

Other Providers

Any PostgreSQL database with pgvector works:

• Neon - Serverless, pgvector built-in
• Supabase - pgvector built-in
• Railway - pgvector available
• AWS RDS - Enable pgvector extension

Design Philosophy

Johnny is intentionally "dumb" - it stores and retrieves without interpreting what memories mean. The consuming application decides:

• What content to store as memories
• How to chunk documents
• What namespace scheme to use
• How to incorporate retrieved memories into prompts
• What similarity thresholds make sense

This keeps Johnny focused and flexible across different use cases.

License

MIT

Part of a growing suite of literary-named MCP servers. See more at github.com/TickTockBent.