Database Patterns

Schema Design

-- Use UUID for distributed-friendly IDs
CREATE EXTENSION IF NOT EXISTS "uuid-ossp";

CREATE TABLE users (
  id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
  email TEXT UNIQUE NOT NULL,
  name TEXT NOT NULL,
  status TEXT NOT NULL DEFAULT 'active'
    CHECK (status IN ('active', 'inactive', 'suspended')),
  metadata JSONB DEFAULT '{}',
  created_at TIMESTAMPTZ DEFAULT NOW(),
  updated_at TIMESTAMPTZ DEFAULT NOW()
);

-- Updated timestamp trigger
CREATE OR REPLACE FUNCTION update_updated_at()
RETURNS TRIGGER AS $$
BEGIN
  NEW.updated_at = NOW();
  RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER users_updated_at
  BEFORE UPDATE ON users
  FOR EACH ROW
  EXECUTE FUNCTION update_updated_at();

Indexing Strategy

-- B-Tree: Equality, range, sorting (default)
CREATE INDEX idx_users_email ON users(email);

-- Composite: Leftmost prefix rule
-- Supports: (user_id), (user_id, created_at)
-- Does NOT support: (created_at) alone
CREATE INDEX idx_orders_user_date ON orders(user_id, created_at DESC);

-- Partial: Reduce index size
CREATE INDEX idx_active_users ON users(email)
  WHERE status = 'active';

-- GIN for JSONB: Containment queries
CREATE INDEX idx_metadata ON users USING GIN (metadata jsonb_path_ops);

-- Expression: Specific JSONB field
CREATE INDEX idx_user_role ON users ((metadata->>'role'));

-- Full-text search
CREATE INDEX idx_search ON products USING GIN (to_tsvector('english', name || ' ' || description));

JSONB Usage

-- Good: Dynamic attributes, rarely queried fields
CREATE TABLE products (
  id UUID PRIMARY KEY,
  name TEXT NOT NULL,
  price NUMERIC(19,4) NOT NULL,
  category TEXT NOT NULL,           -- Extracted: frequently queried
  attributes JSONB DEFAULT '{}'     -- Dynamic: color, size, specs
);

-- Query with containment
SELECT * FROM products
WHERE category = 'electronics'              -- B-Tree index
  AND attributes @> '{"brand": "Apple"}';   -- GIN index

-- Query specific field
SELECT * FROM products
WHERE attributes->>'color' = 'black';       -- Expression index

-- Update JSONB field
UPDATE products
SET attributes = attributes || '{"featured": true}'
WHERE id = '...';

Query Optimization

-- Always use EXPLAIN ANALYZE
EXPLAIN ANALYZE
SELECT u.*, COUNT(o.id) as order_count
FROM users u
LEFT JOIN orders o ON o.user_id = u.id
WHERE u.status = 'active'
GROUP BY u.id
ORDER BY u.created_at DESC
LIMIT 20;

-- Watch for:
-- ❌ Seq Scan on large tables → Add index
-- ❌ Sort → Use index for ordering
-- ❌ Nested Loop with many rows → Consider JOIN order
-- ❌ Hash Join on huge tables → Add indexes

Connection Pooling

// PgBouncer or built-in pool
import { Pool } from 'pg';

const pool = new Pool({
  max: 20,                      // Max connections
  idleTimeoutMillis: 30000,     // Close idle connections
  connectionTimeoutMillis: 2000, // Fail fast
});

// Connection count formula:
// connections = (cores * 2) + effective_spindle_count
// Usually 10-30 is enough

Redis

Data Structure Selection

Key Naming

# Format: <entity>:<id>:<attribute>