Databases

Every database connection has a cost. TCP handshake, TLS negotiation, authentication, session setup—all before your first query runs. For PostgreSQL, that’s typically 20-50ms. For a single request, barely noticeable. For thousands of requests per second, catastrophic. Connection pooling solves this by maintaining a set of pre-established connections that your application reuses. Done right, it’s one of the highest-impact performance optimizations you can make. The Problem: Connection Overhead Without pooling, every request cycle looks like this: ...

Database migrations are the scariest part of deployments. Get them wrong and you’re looking at downtime, data loss, or a 3 AM incident call. Here’s how to migrate safely. The Problem Naive migrations cause problems: 1 2 3 4 5 6 -- This locks the entire table ALTER TABLE users ADD COLUMN phone VARCHAR(20) NOT NULL; -- 10 million rows, exclusive lock held for minutes -- Application queries queue up -- Users see errors Safe Migration Patterns Adding Columns Bad: Adding NOT NULL column without default ...

Your query is slow. You add an index. It gets faster. Magic, right? Not quite. Indexes are powerful but misunderstood. Used well, they turn seconds into milliseconds. Used poorly, they slow down writes, waste storage, and sometimes make queries slower. Let’s demystify them. What Is an Index? An index is a separate data structure that helps the database find rows without scanning the entire table. Think of it like a book’s index—instead of reading every page to find “PostgreSQL,” you look it up in the index and jump directly to page 247. ...

Every database connection costs something: TCP handshake, TLS negotiation, authentication, session state allocation. For PostgreSQL, that’s 1.3-2MB of memory per connection. For MySQL, 256KB-1MB. At scale, creating connections on demand kills both your database and your latency. Connection pooling solves this by reusing connections across requests. But misconfigured pools are worse than no pools — you get connection starvation, deadlocks, and debugging nightmares. Here’s how to do it right. The Problem: Connection Overhead Without pooling, a typical web request: ...

A practical guide to database migrations — tools, patterns, and strategies for evolving your schema safely in production.