CONCEPT Cited by 1 source
Amazon Time Sync attribution¶
Amazon Time Sync is AWS's fleet-wide time-synchronisation service, exposed as a local NTP/PTP endpoint on Nitro-based EC2 instances. It provides sub-millisecond accuracy across the fleet, making wall-clock time ranges a reliable attribution key.
Why this matters for attribution¶
Heartbeat-based ownership
represents the owner of a resource as a list of
(owner, t_start, t_end) time ranges, and attribution is done by
looking up the query's timestamp against the range list. This
design depends on the following being true:
- The timestamp on an observation (the flow's
t_start/t_end) was taken on a clock that agrees with the clock used to stamp heartbeats to within the granularity needed. - Two hosts reporting the same resource's ownership can agree on the ordering of transition events.
If host-level clocks drifted by even hundreds of milliseconds, the time-range lookup would straddle boundaries or miss the correct range — misattributions and unattributions would multiply. Amazon Time Sync's sub-ms accuracy makes the clock a non-issue for AWS-hosted fleets.
"Since Netflix uses Amazon Time Sync across its fleet, the timestamps (captured by FlowExporter) are reliable."
Boundary¶
- Across AWS regions. Amazon Time Sync is regional; cross-region traffic relies on the fact that all regions ultimately reference the same atomic-clock source, but clock-comparison-across-regions has higher uncertainty. Netflix's cross-regional attribution path uses forwarding + regional time-range lookup, so the lookup happens in the target region's clock frame.
- Across cloud providers. Not a concern for AWS-native Netflix.
Seen in¶
- sources/2025-04-08-netflix-how-netflix-accurately-attributes-ebpf-flow-logs — named as the load-bearing substrate making heartbeat attribution by time range reliable.