Number

Gapless, per-period invoice numbering is a legal requirement in the DACH market, and it is a race condition waiting to happen. Modules ask this service for the next number in a scope instead of each re-implementing a careful counter. Allocation is a single atomic transaction, so concurrent callers never receive a duplicate and never skip a value. A scope’s format renders the number from tokens — {seq}, zero-padded {seq:0000}, {YYYY}, {YY}, {MM}, {DD} — and its period restarts the counter each year, month or day, or never.

Responsibilities

• Independent counters per scope (invoice, order, offer, purchase order…)
• Atomic allocation — no duplicates and no gaps under concurrency
• Token-based formatting, e.g. INV-{YYYY}-{seq:0000} → INV-2026-0001
• Period reset by year, month or day; gapless within the period
• A sensible default format auto-created for an unknown scope

API surface

• POST /api/next
• GET/POST /api/sequences · GET /api/sequences/:scope
• GET /api/health · GET /api/ready · GET /api/metrics

CONSUMED BY MOD-04 Invoice & Billing, MOD-13 Offers, MOD-06 Procurement, MOD-07 Storefront. A Platform Service never depends on a Business Module.