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Notification Template Architecture

Summary​

Templates are per-channel subject/body pairs, resolvable per tenant and versioned. Resolution prefers a tenant-specific active template over the global default and picks the highest active version. Rendering substitutes {{Variable}} placeholders, leaving unknown placeholders empty.

Resolution precedence​

Template model​

NotificationTemplate carries a nullable TenantId (null = global/system default), a TemplateKey (usually the source event type), a Channel, a monotonic Version, subject and body templates, an optional Locale, an IsActive flag and a description. A unique index enforces one row per (TenantId, TemplateKey, Channel, Version).

Rendering​

TemplateEngine uses a compiled regex ({{ Name }}) to replace placeholders from the supplied variable dictionary. Missing variables render as empty strings so a partial payload never blocks a notification. Render also supports rendering arbitrary subject/body text, used by the template test endpoint.

Default seeding​

DefaultTemplateSeeder inserts built-in global (null-tenant) templates — one per event/channel — when they are missing. Seeding is idempotent: a (null, key, channel) row that already exists is skipped. The inventory covers employee, leave, payroll, document, tenant-provisioning, expense, asset, performance, training/LMS and helpdesk keys across in-app and email channels.

Template management surface​

The API exposes template list, create-next-version, in-place update and a test-render (optionally live-send) endpoint. Creating a template computes the next Version for its (tenant, key, channel).

Verified constraints​

  • Locale exists on the model but is not used by resolution (invariant rendering only).
  • There is no separate TemplateRenderer service or templating engine beyond the regex substitution.
  • The extracted-service template model differs from the legacy monolith template model (documented under compatibility).

Requires Confirmation​

Localization strategy, template approval/versioning governance and the canonical template system across the two implementations require confirmation.

Source References​

  • microservices/src/notification-service/Application/TemplateEngine.cs
  • microservices/src/notification-service/Domain/NotificationEntities.cs
  • microservices/src/notification-service/Seed/DefaultTemplateSeeder.cs
  • microservices/src/notification-service/Api/NotificationEndpoints.cs

See Also​

Keywords​

Templates, rendering, versioning, placeholders, seeding, precedence.

Revision Information​

  • Status: Draft
  • Last reviewed: 2026-07-21
  • Next review: 2026-10-21