== Transfer Performance Issue ==
Cross-region data replication from us-east-1 to ap-southeast-1 extremely slow.

== Observed Throughput ==
aws s3 cp 1gb-file.bin s3://dest-bucket-ap-southeast-1/
Completed 1.0 GiB/1.0 GiB (3.2 MiB/s) with 1 file(s) remaining

Expected throughput: ~50-100 MiB/s based on link capacity
Actual throughput: 3.2 MiB/s (30x slower than expected)

== Network Diagnostics ==
Ping from us-east-1 EC2 to ap-southeast-1 S3 endpoint:
  PING s3.ap-southeast-1.amazonaws.com: min=185ms avg=192ms max=210ms

iperf3 bandwidth test (us-east-1 to ap-southeast-1):
  Transfer: 10.0 GiB  Bitrate: 1.05 Gbits/sec

== RTT Analysis ==
Round-trip time (RTT): ~192ms
TCP window size: default (not tuned for high-latency WAN)
Bandwidth-delay product: 1000 Mbps × 0.192s = 24 MB unacknowledged data in flight
Actual TCP window: ~64 KB (default, not scaled)

== Transfer Details ==
Single-threaded transfer: 3.2 MiB/s
AWS CLI multipart threshold: 8 MB (default)
File size: 1 GB
Multipart part size: 8 MB

== s5cmd Parallel Test ==
s5cmd --numworkers 256 cp 1gb-file.bin s3://dest-bucket-ap-southeast-1/
Throughput: 87 MiB/s  (27x improvement)
