Builder

Constructs a complex object step by step, separating construction logic from the object's final representation — avoids telescoping constructors with many optional parameters.

Why we need this / what value this brings

Makes constructing a complex object readable and safe, avoiding a constructor with 8 positional boolean/optional parameters that are easy to mix up.

When to use this

An object has many optional parameters or must be constructed in a specific multi-step sequence.

How to use or implement this

Chain method calls that each set one piece of the object, ending in a .build(); in Python, keyword-only arguments or a Pydantic model often achieve the same goal more simply.

Research questions

• Any place in Localz's backend where a function takes 6+ optional parameters would benefit from a builder (or, in Python, keyword-only args / a Pydantic model) instead.
• See Builder Pattern's "Common pitfall" section — a builder is only worth the ceremony if .build() actually centralizes cross-field validation; check whether any candidate site found above has that kind of validation need before introducing one.