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.
Reference: APM Traces and Spans
