The Internet Archive rate-limits the Wayback Machine to protect
their infrastructure. Any client that fires requests too quickly
from a single IP — a browser on an aggressive script, a
command-line downloader with concurrency turned up, or many
people sharing one network — will hit HTTP 429 and either stall or get empty responses.
Fixes in order of effort: wait and retry with exponential backoff,
throttle to roughly one request per second, or hand the job to a
server-side tool that already handles polite backoff.
Full fix list: the 429 guide.