Worker Engine

Architecture: Hybrid Hangfire + SQS Strategy

The background worker operates in a highly-concurrent hybrid capacity targeting reliability and idempotency:

Layer	Engine	Purpose
Scheduled Jobs	Hangfire (PostgreSQL Backed)	Recurring cron-based polling routines (Price Sync, Metrics Refresh, News Batching).
Event Handlers	Amazon SQS + Redis	Reactive tasks triggered by API events (price alerts, low holdings, news on-demand).
Real-time Push	SignalR + Redis Backplane	Instant delivery of detected alerts from Worker to UI.

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Scheduled Job Catalog

Running inside InventoryAlert.Worker, driven by Hangfire cron schedules.

Schedules are configurable via WorkerSettings.Schedules.* (with sensible defaults in code and environment overrides via appsettings*.json).

InventoryAlert uses a total of 6 background jobs (5 recurring via Hangfire + 1 continuous SQS listener), optimized for active ticker scoping and Finnhub 60 req/min rate limits.

Job	Schedule setting	Finnhub Endpoint	Key duty
SyncPricesJob	*/15 * * * *	/quote	Active symbol fetch → insert PriceHistory → evaluate AlertRule → insert Notification → SignalR push
SyncStockFundamentalsJob	10 6 * * *	/metric, /earnings, /recommendation, /insider-transactions	Consolidated daily sync for basic financials, quarterly earnings, analyst recommendations, and SEC insider trades for active symbols
NewsSyncJob	5 */2 * * *	/news & /company-news	Consolidated market + active company news batch sync to DynamoDB read models
CleanupPriceHistoryJob	20 2 * * *	—	Deletes PriceHistory rows older than 1 year to keep PostgreSQL lean
ProcessQueueJob	Continuous Poller	—	Native SQS poller + router + Redis idempotency
KeepAliveJob	*/10 * * * *	—	Self-pings http://127.0.0.1:8080/healthz to guarantee 24/7 Render free-tier container uptime

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The Optimized Evaluation Pipeline: SyncPricesJob

The current architecture uses high-concurrency quote fetching and batch rule evaluation:

1. Collect active TickerSymbols from StockListing.
2. PART 1 (Parallel Sync):
   - Fetch Finnhub /quote in parallel (MaxDegreeOfParallelism=5).
   - Batch insert into PriceHistory using AddRangeAsync.
3. PART 2 (Batch Alert Check):
   - Fetch all active AlertRules for processed symbols in ONE query.
   - Evaluate breach conditions (direct comparison or cost-basis math).
4. PART 3 (Real-time Notification):
   - Batch insert Notification records.
   - For each breach: Push via `IAlertNotifier` (SignalR via Redis backplane).
5. COMMIT: Single SaveChangesAsync call for all history, notifications, and rule updates.

Key Performance Highlights

• Parallel I/O: Reduces sync time by fetching multiple quotes simultaneously.
• N+1 Avoidance: Repository-level batch fetching for alert rules.
• Backplane Delivery: Alert detection in Worker triggers Hub delivery in Api instantly via Redis.

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Event Handlers (SQS Topology)

Located in IntegrationEvents/Handlers, invoked by IntegrationMessageRouter after messages are pulled from SQS by ProcessQueueJob.

Handler	SQS Event Type	Role
MarketPriceAlertHandler	inventoryalert.pricing.price-drop.v1	Evaluate rules for a specific symbol + price payload and push notifications
LowHoldingsHandler	inventoryalert.inventory.stock-low.v1	Persist + push a holdings notification for a specific user + symbol
NewsSyncJob (via Router)	inventoryalert.news.sync-requested.v1	Enqueue the consolidated news sync job
DefaultHandler	* (unmatched)	Log + acknowledge (prevents poison-message blockage)

Notes:

• inventoryalert.news.company-sync-requested.v1 is defined in EventTypes, but is not currently routed by IntegrationMessageRouter.

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Health Monitoring

The worker is equipped with health check endpoints exposed via HTTP (port 8080 internally, 8081 in Docker Compose):

• Liveness & Readiness: GET /health
• Dependency Checks: Verified connectivity to PostgreSQL on startup.
• Docker Integration: Configured with interval: 10s and retries: 5 to ensure background services stay responsive.