Prefer Structured URLs Over Flat URLs

Context

URL design is often treated as a purely aesthetic or SEO decision. Teams favor "clean" flat URLs like /nike-air-zoom over structured URLs like /product/nike-air-zoom. However, flat URLs have significant architectural costs that are often overlooked.

With flat URLs, applications cannot determine the entity type from the path alone, requiring resolution queries:

// Flat URL - requires resolution
const slug = path.split('/')[1];

const product = await getProduct(slug);
if (product) return renderProduct(product);

const category = await getCategory(slug);
if (category) return renderCategory(category);

return render404();

With structured URLs, routing is deterministic — no resolution needed:

// Structured URL - instant routing
const prefix = path.split('/')[1]; // "product"
// Route directly to product handler

A case study documented the real-world impact: every page required 2 backend calls (one succeeds, one fails), 404s wasted 2 calls each, and infrastructure costs were 40% higher than projected.

Flat URLs also require enforcing slug uniqueness across all entity types at the database level — a product and category cannot share the same slug. Structured URLs allow independent namespaces per type.

Resolution

• You SHOULD use structured/prefixed URLs for new projects (e.g., /p/slug or /product/slug).

Links

• The Hidden Cost of URL Design - Case study referenced in Context