In Application Performance Monitoring (APM), where is the span context information located during transfer?

In OCI APM, span context (e.g., Trace ID, Span ID) is propagated across services to track requests.

In HTTP header (B): Span context is embedded in HTTP headers (e.g., X-B3-TraceId) during transfer between services. This allows APM to correlate spans across distributed systems for a single user request.

Why not A, C, or D?

Service boundaries (A): This is a conceptual term, not a location for data.

HTTP call (C): Too vague—“HTTP call” isn’t a specific storage location.

Browser and microservices (D): Context originates here but is transferred via headers, not stored locally during transit.

This follows the OpenTracing standard used by OCI APM.