A practical guide to typed configuration

Configuration sits between human-friendly text and code that needs guarantees. A useful pipeline keeps those concerns separate: parse, validate, then expose a typed value.

Validate at the boundary

const config = ConfigSchema.parse({
  port: process.env.PORT,
  databaseUrl: process.env.DATABASE_URL,
})

After this line, application code should consume config rather than reading environment variables again.

Make defaults visible

A default changes behavior, so treat it as part of the public contract. Document it next to the schema and cover it with a focused test.

Inline expressions such as $timeout = 2^n$ are useful for explaining backoff rules without separating the mathematics from the prose.