Architecture

1. System Context (C4 L1)

2. Container View (C4 L2)

3. Mode-Based Deployment

Controlled by APP_ENV_MQ_PAY_MODE. Source: @nx/mq-pay/src/common/constants.ts:11-14.

Mode	Controllers	Queue producer	Worker	Production pattern
FULL (default)	✓	✓	✓	Dev / single-instance
API	✓	✓	✗	One pod, scale REST horizontally
WORKER	✗	✗	✓	N pods, each with unique Snowflake ID (91, 92, …)

4. Component View (C4 L3)

5. Runtime Scenarios

5.1 Boot — MQ-Pay wiring

5.2 IPN → Event → Webhook + WS

5.3 Per-merchant credential lookup

6. Crosscutting Concerns

Concern	Handling
Encryption	CryptoUtility (AES-256-GCM) + secret from APP_ENV_APPLICATION_SECRET; payment provider credentials encrypted at rest
Mode-based deployment	APP_ENV_MQ_PAY_MODE ∈ {FULL, API, WORKER}; ApplicationPaymentComponent binds options accordingly
AuthN	JWT (verified locally via JWKS from identity); IPN endpoints have provider-signature verification (in MQ-Pay)
AuthZ	Casbin via PolicyDefinitionService; permissions cached
Idempotency	WebhookEventHandlerHelper skips webhook dispatch for non-actionable events (CREATED/SENT); subscriber-side dedup recommended
Logging	IGNIS structured (key: %s); event type + transaction id in every line
Soft-delete	WebhookConfig soft-deletable; Configuration soft-deletable
IDs	Snowflake; FULL=4, API=8, WORKER=91+

7. Related Pages

• Domain Model
• Integration — MQ-Pay + sale + subscribers
• API Events — full webhook + WS catalogue
• Webhook Dispatch
• Provider Credentials
• Decisions