External Service Integrations

How InventoryAlert communicates with third-party APIs and external services.

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Finnhub API

• Purpose: Real-time stock quote data, company metadata, and analytics (earnings, recommendations, insiders, peers)
• Auth: API key via ?token={API_KEY} query param (from FINNHUB_API_KEY env / appsettings.json → Finnhub:ApiKey)
• Rate Limits: 60 requests/minute on free tier. Internal cap set at 55 rpm via Redis counter finnhub:ratelimit.

Endpoints Used

Finnhub Endpoint	Our Route	Called By
GET /api/v1/quote	GET /stocks/{symbol}/quote	StockDataService
GET /api/v1/stock/profile2	GET /stocks/{symbol}/profile	StockDataService
GET /api/v1/stock/market-status	GET /market/status	StockDataService
GET /api/v1/news	GET /market/news	NewsSyncJob (sync) + StockDataService (read)
GET /api/v1/company-news	GET /stocks/{symbol}/news	NewsSyncJob (sync) + StockDataService (read)
GET /api/v1/search	GET /stocks/search	Discovery flow
GET /api/v1/stock/metric	GET /stocks/{symbol}/financials	SyncMetricsJob
GET /api/v1/stock/earnings	GET /stocks/{symbol}/earnings	SyncEarningsJob
GET /api/v1/stock/recommendation	GET /stocks/{symbol}/recommendation	SyncRecommendationsJob
GET /api/v1/stock/insider-transactions	GET /stocks/{symbol}/insiders	SyncInsidersJob
GET /api/v1/stock/peers	GET /stocks/{symbol}/peers	StockDataService
GET /api/v1/calendar/earnings	GET /market/calendar/earnings	StockDataService
GET /api/v1/calendar/ipo	GET /market/calendar/ipo	StockDataService
GET /api/v1/stock/market-holiday	GET /market/holiday	StockDataService

Quote Response Mapping

// Finnhub /quote Response
{
  "c": 172.50,    // currentPrice
  "d": -2.30,     // change
  "dp": -1.32,    // changePercent
  "h": 175.00,    // high
  "l": 170.10,    // low
  "o": 173.00,    // open
  "pc": 174.80,   // prevClose
  "t": 1713000000 // timestamp
}

Error Handling Rules

• If c (current price) is null or 0 → skip that symbol, log warning, continue loop.
• If Finnhub returns an HTTP error → log and skip, never throw.
• Quotes are cached in Redis for 30 seconds (quote:{symbol}).

// IFinnhubClient contract
if (quote?.CurrentPrice is null or 0) return null; // skip — free tier limitation

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Amazon SQS

• Purpose: Async event bus between InventoryAlert.Api / InventoryAlert.Worker
• Local Emulation: Moto running in Docker at http://moto:5000
• Configuration: Aws:SqsQueueUrl in appsettings.Docker.json

Queues

Queue	Purpose	Publisher	Consumer
inventory-events	Domain event bus	Api, Worker	Worker (IntegrationMessageRouter)
inventory-events-dlq	Dead letter queue	SQS (auto-redrive after 5 failures)	Manual replay via Hangfire / AWS Console

Consumer Pattern

// ProcessQueueJob — long-polling
var messages = await _sqsHelper.ReceiveMessagesAsync(queueUrl, maxMessages: 10, ct: ct);

• Visibility Timeout: 30 seconds (message hidden from other consumers while processing)
• Max Receive Count: 5 — after 5 failures, message is moved to DLQ automatically
• Long-polling Wait: 20 seconds per poll cycle to reduce empty-response API calls

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Amazon DynamoDB

• Purpose: Permanent storage for high-volume news data (never deleted, queryable by range)
• Local Emulation: Same Moto container as SQS (http://moto:5000)

Tables

Table	PK	SK	GSI
inventoryalert-market-news	CATEGORY#<category>	TS#<unix_ms>	—
inventoryalert-company-news	SYMBOL#<ticker>	TS#<unix_ms>	BySymbolAndDate (Symbol, SK)

Access Patterns

• Write: PutItemAsync on news fetch. Deduplication by NewsId attribute before insert.
• Read (Market News): QueryAsync with PK CATEGORY#general, SK range from TS#{30_days_ago} to TS#{now}.
• Read (Company News): QueryAsync with PK SYMBOL#TSLA, sorted descending, limit 20.

No TTL: News is retained indefinitely as a historical archive. Use SK range filters to retrieve recent articles.

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Redis

• Purpose: Quote caching, SQS idempotency markers, alert cooldown
• Local: localhost:6379 (Docker: inventory-cache)
• Namespaces:

Key	TTL	Purpose
quote:{symbol}	30s	Cached Finnhub quote
msg:processed:{messageId}	24h	SQS idempotency marker (written after successful processing)
inventoryalert:alerts:cooldown:v1:{userId}:{ruleId}	24h	Alert cooldown gate (per user + rule)