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_docs/02_document/deployment/observability.md

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+# Observability
+
+## Logging
+
+| Aspect | Implementation |
+|--------|---------------|
+| Framework | Serilog 4.1.0 |
+| Sinks | Console, Rolling File (`logs/log.txt`, daily) |
+| Minimum Level | Information |
+| Enrichment | `FromLogContext` |
+
+### Log Sources
+
+| Source | Level | Content |
+|--------|-------|---------|
+| BusinessExceptionHandler | WARN | Business exceptions with message |
+| ResourcesService | INFO | Successful file saves |
+| DbFactory (linq2db trace) | INFO | SQL query text (via `Console.WriteLine`) |
+
+## Metrics
+
+No metrics collection configured (no Prometheus, Application Insights, or similar).
+
+## Health Checks
+
+No health check endpoint configured.
+
+## Tracing
+
+No distributed tracing configured.
+
+## Observations
+
+- Logging is minimal — no structured request/response logging.
+- No health check endpoint for container orchestration or load balancer probes.
+- SQL trace goes directly to `Console.WriteLine`, not through Serilog.
+- No log correlation (request IDs, trace IDs).
+- No alerting or monitoring infrastructure.