On AWS the metadata service is rate limited. The code below overloads the system pretty fast, returning an HTTP 429 error code

overload.sh

#!/bin/sh
set -e

ZONE=$(curl http://169.254.169.254/latest/meta-data/placement/availability-zone 2>/dev/null)

failed() {
    echo Failed after ${X}
    exec curl http://169.254.169.254/latest/meta-data/placement/availability-zone
}

trap failed EXIT

for X in {1..5000}; do
    curl http://169.254.169.254/latest/meta-data/placement/availability-zone 2>/dev/null | grep ${ZONE}  > /dev/null
done
echo Done