PostgreSQL vs MySQL: When to Use Which?

As a developer, databases are the foundation of almost every application. PostgreSQL and MySQL are both popular, but their characteristics differ. This article will help you choose the right one for your project.

Quick Overview

PostgreSQL: The Feature-Rich Database

PostgreSQL (or “Postgres”) is a relational database known for its advanced features and standards compliance. Developed since 1996, Postgres has a reputation as a powerful database for complex use cases.

-- PostgreSQL supports rich data types
CREATE TABLE products (
  id SERIAL PRIMARY KEY,
  name VARCHAR(255),
  metadata JSONB,           -- Native JSON with indexing
  tags TEXT[],              -- Native array support
  price NUMERIC(10,2),
  created_at TIMESTAMPTZ DEFAULT NOW()
);

Philosophy: Extensibility and strict SQL compliance.

MySQL: The Reliable Workhorse

MySQL is the most popular relational database in the world. Acquired by Oracle, it also has a popular fork called MariaDB. MySQL is known for its simplicity and reliability.

-- MySQL straightforward syntax
CREATE TABLE products (
  id INT AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(255),
  metadata JSON,
  price DECIMAL(10,2),
  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

Philosophy: Simple, fast, and reliable for web applications.

Feature Comparison Table

Feature	PostgreSQL	MySQL
ACID Compliance	✅ Full ACID	✅ Full ACID (InnoDB)
JSON Support	JSONB with indexing	JSON (no native indexing)
Full-Text Search	✅ Built-in excellent	✅ Built-in basic
Replication	Streaming, logical	Master-slave, group
Stored Procedures	PL/pgSQL, Python, etc	SQL/PSM
Extensions	✅ Highly extensible	❌ Limited
CTE (WITH clause)	✅ Recursive support	✅ Since MySQL 8.0
Window Functions	✅ Complete	✅ Since MySQL 8.0
UPSERT	ON CONFLICT	ON DUPLICATE KEY
Partial Indexes	✅ Yes	❌ No
GIS/Spatial	PostGIS (excellent)	Spatial (basic)

Deep Dive: ACID Compliance

Both support ACID, but there are important nuances:

PostgreSQL

• ACID compliance by default
• Mature MVCC (Multi-Version Concurrency Control)
• Complete isolation levels including Serializable

MySQL

• ACID compliance only with InnoDB engine
• MyISAM (legacy engine) is not ACID compliant
• Default isolation level: REPEATABLE READ

-- PostgreSQL: Check isolation level
SHOW transaction_isolation;
-- Default: read committed

-- MySQL: Check isolation level  
SELECT @@transaction_isolation;
-- Default: REPEATABLE-READ

Deep Dive: JSON Support

This is one of the biggest differences and often a deciding factor.

PostgreSQL JSONB

-- PostgreSQL: JSONB with GIN indexing
CREATE TABLE orders (
  id SERIAL PRIMARY KEY,
  data JSONB
);

-- Create index on JSONB field
CREATE INDEX idx_orders_data ON orders USING GIN (data);

-- Query nested JSON with operators
SELECT * FROM orders 
WHERE data @> '{"status": "completed"}';

-- Update nested field
UPDATE orders 
SET data = jsonb_set(data, '{shipping,address}', '"New York"')
WHERE id = 1;

MySQL JSON

-- MySQL: JSON without native indexing
CREATE TABLE orders (
  id INT AUTO_INCREMENT PRIMARY KEY,
  data JSON
);

-- Query JSON field
SELECT * FROM orders 
WHERE JSON_EXTRACT(data, '$.status') = 'completed';

-- Or with shorthand
SELECT * FROM orders 
WHERE data->>'$.status' = 'completed';

-- Update nested field
UPDATE orders 
SET data = JSON_SET(data, '$.shipping.address', 'New York')
WHERE id = 1;

Verdict: PostgreSQL JSONB is far more powerful for JSON-heavy applications. Indexing and querying are more efficient.

Deep Dive: Replication

PostgreSQL Replication

-- Streaming Replication (physical)
-- in postgresql.conf
wal_level = replica
max_wal_senders = 3

-- Logical Replication (table-level)
CREATE PUBLICATION my_pub FOR TABLE users, orders;
CREATE SUBSCRIPTION my_sub 
CONNECTION 'host=primary dbname=app' 
PUBLICATION my_pub;

Advantages:

• Logical replication for selective table sync
• Synchronous replication option
• pg_basebackup for backup

MySQL Replication

-- Binary Log Replication
-- in my.cnf
server-id = 1
log_bin = mysql-bin

-- Setup replica
CHANGE REPLICATION SOURCE TO
  SOURCE_HOST='primary',
  SOURCE_USER='repl',
  SOURCE_PASSWORD='password';
START REPLICA;

Advantages:

• More straightforward setup
• Group Replication for high availability
• MySQL Router for load balancing

Deep Dive: Extensions

This is a game changer for PostgreSQL.

PostgreSQL Extensions

-- PostGIS for geospatial
CREATE EXTENSION postgis;
SELECT ST_Distance(
  ST_GeomFromText('POINT(-73.9857 40.7484)'),  -- New York
  ST_GeomFromText('POINT(-118.2437 34.0522)')   -- Los Angeles
);

-- pg_trgm for fuzzy search
CREATE EXTENSION pg_trgm;
SELECT * FROM products 
WHERE name % 'samsu'  -- Matches "Samsung"
ORDER BY similarity(name, 'samsu') DESC;

-- uuid-ossp for UUID
CREATE EXTENSION "uuid-ossp";
SELECT uuid_generate_v4();

-- timescaledb for time-series
CREATE EXTENSION timescaledb;

MySQL doesn’t have an extension system like this. Features must be built-in or use external tools.

Performance Comparison

Scenario	PostgreSQL	MySQL
Read-heavy, simple queries	Good	⚡ Slightly faster
Write-heavy	⚡ Better	Good
Complex queries	⚡ Much better	Adequate
JSON operations	⚡ Very fast	Slow
Full-text search	⚡ Excellent	Basic
Concurrent writes	⚡ MVCC superior	Good

Note: Performance differences are often marginal for typical workloads. Choose based on features, not micro-benchmarks.

Important Syntax Differences

Auto Increment

-- PostgreSQL
CREATE TABLE users (
  id SERIAL PRIMARY KEY,      -- or BIGSERIAL
  name TEXT
);

-- Modern alternative (PostgreSQL 10+)
CREATE TABLE users (
  id INTEGER GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
  name TEXT
);

-- MySQL
CREATE TABLE users (
  id INT AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(255)
);

UPSERT (Insert or Update)

-- PostgreSQL: ON CONFLICT
INSERT INTO users (email, name) 
VALUES ('john@example.com', 'John')
ON CONFLICT (email) 
DO UPDATE SET name = EXCLUDED.name;

-- MySQL: ON DUPLICATE KEY
INSERT INTO users (email, name) 
VALUES ('john@example.com', 'John')
ON DUPLICATE KEY UPDATE name = VALUES(name);

String Concatenation

-- PostgreSQL
SELECT first_name || ' ' || last_name AS full_name FROM users;

-- MySQL
SELECT CONCAT(first_name, ' ', last_name) AS full_name FROM users;

Boolean

-- PostgreSQL: Native boolean
CREATE TABLE posts (
  id SERIAL PRIMARY KEY,
  is_published BOOLEAN DEFAULT FALSE
);

-- MySQL: Uses TINYINT (1/0)
CREATE TABLE posts (
  id INT AUTO_INCREMENT PRIMARY KEY,
  is_published TINYINT(1) DEFAULT 0
);

LIMIT with OFFSET

-- PostgreSQL
SELECT * FROM products LIMIT 10 OFFSET 20;

-- MySQL (same, but also supports)
SELECT * FROM products LIMIT 20, 10;  -- LIMIT offset, count

Popular Managed Services

PostgreSQL

Service	Highlight
Supabase	Firebase alternative, realtime, auth built-in
Neon	Serverless, branching, generous free tier
Railway	Simple deployment, good DX
Render	Easy setup, auto-scaling
AWS RDS	Enterprise, highly configurable
DigitalOcean	Affordable managed database

MySQL

Service	Highlight
PlanetScale	Serverless, branching, Vitess-powered
AWS RDS	Enterprise, Aurora compatible
DigitalOcean	Simple managed MySQL
Railway	Easy deployment
Aiven	Multi-cloud support

Managed Services Recommendations

For startups/side projects:

• PostgreSQL → Supabase or Neon
• MySQL → PlanetScale

For serious production:

• PostgreSQL → AWS RDS or Neon
• MySQL → PlanetScale or AWS Aurora

Use Cases

Choose PostgreSQL for:

1. Applications with complex data

   • JSON-heavy applications
   • Geospatial (maps, location)
   • Time-series data

2. Analytics and reporting

   • Complex queries
   • Window functions
   • Complex CTEs

3. Fintech and banking

   • Strict ACID
   • Data integrity is paramount
   • Audit trail

4. Full-text search

   • Built-in tsvector
   • Trigram matching
   • Language-aware stemming

Choose MySQL for:

1. Standard web applications

   • Blog, CMS, e-commerce
   • CRUD operations
   • Read-heavy workloads

2. Legacy systems

   • Many PHP apps use MySQL
   • WordPress, Drupal, Magento
   • Existing MySQL expertise

3. High-read scenarios

   • Caching-friendly
   • Read replicas
   • CDN-backed content

4. Simplicity is priority

   • Quick setup
   • Familiar syntax
   • Abundant tutorials

Recommendations by Project Type

Project Type	Recommendation	Reason
Personal Blog	Either	Both are overkill, choose what’s familiar
SaaS Startup	PostgreSQL	Flexibility to pivot
E-commerce	Either	MySQL proven, PostgreSQL more features
Fintech	PostgreSQL	Strict ACID, better data types
Analytics	PostgreSQL	Complex queries, window functions
CMS (WordPress)	MySQL	Native support
Geospatial App	PostgreSQL	PostGIS is unbeatable
Real-time App	PostgreSQL	LISTEN/NOTIFY, Supabase realtime
IoT/Time-series	PostgreSQL	TimescaleDB extension
Microservices	Either	Depends on service needs

ORM & Driver Support

Both have excellent support in all popular languages:

Node.js

// PostgreSQL with Prisma
const { PrismaClient } = require('@prisma/client');
const prisma = new PrismaClient();

// datasource in schema.prisma
// provider = "postgresql"

// MySQL with Prisma
// provider = "mysql"

Drizzle ORM

// PostgreSQL
import { drizzle } from 'drizzle-orm/node-postgres';
import { Pool } from 'pg';

const pool = new Pool({ connectionString: process.env.DATABASE_URL });
const db = drizzle(pool);

// MySQL
import { drizzle } from 'drizzle-orm/mysql2';
import mysql from 'mysql2/promise';

const connection = await mysql.createConnection(process.env.DATABASE_URL);
const db = drizzle(connection);

Migration from One to Another

If you need to migrate:

MySQL → PostgreSQL

Tools:

• pgloader (recommended)
• AWS DMS
• Manual with CSV export/import

# Using pgloader
pgloader mysql://user:pass@localhost/mydb \
         postgresql://user:pass@localhost/mydb

PostgreSQL → MySQL

More challenging because:

• Different data types (JSONB, arrays)
• Features that don’t exist in MySQL
• Syntax differences

Tools:

• AWS DMS
• Custom scripts
• Manual conversion

Conclusion

PostgreSQL is the right choice if:

• You need advanced features (JSONB, arrays, extensions)
• Complex data model
• Priority: flexibility and feature-richness
• Using Supabase or Neon

MySQL is the right choice if:

• Standard web application
• Team is familiar with MySQL
• Simple CRUD operations
• Using PlanetScale or existing MySQL infra

TL;DR Decision Tree

Need JSONB/Geospatial? → PostgreSQL
Using WordPress/PHP legacy? → MySQL
Startup needing flexibility? → PostgreSQL
Simple web app? → Either (choose what's familiar)
Using Supabase? → PostgreSQL
Using PlanetScale? → MySQL

Ultimately, both are excellent databases. The best choice is one that fits:

1. Your project’s technical requirements
2. Your team’s expertise
3. Your existing ecosystem

---

Have questions about PostgreSQL or MySQL? Reach out on Twitter @nayakayp!