"Within a minute" is mostly marketing. Google's Indexing API is officially only for JobPosting and BroadcastEvent schema, but in practice it works on any URL with around 40-60% success within 24-48 hours, not 1 minute.
I run a self-hosted indexer (Node + service account rotation) and the real bottleneck isn't submission speed, it's quota. Each Google Cloud project caps at 200 URLs/day. If you want to push 10K+ links a month you'll need 40-50 service accounts rotating, otherwise you hit the wall fast. That's literally what the paid bulk indexers are doing behind the scenes.
Realistic expectation: 40-50% indexed in week 1, 60-70% by week 3-4 with re-submission. Anyone promising 90%+ in minutes is either lying or testing on already-crawled URLs.