op.TimeToResponseNS = since.Nanoseconds()
			globalTierMetrics.Observe(tier, since)
			globalTierMetrics.logSuccess(tier)
		} else {
			op.Error = err.Error()
			globalTierMetrics.logFailure(tier)
		}

		logger.GetReqInfo(ctx).AppendTags("tierStats", op.String())
	}
}

// getTransitionedObjectReader returns a reader from the transitioned tier.