Short answer: a backlink on a page Google has not indexed is not doing anything for you yet. It may later, when the page is indexed, or never, if it is not. The question is usually answered with opinion, so we measured it on our own money.
Between 28 August and 1 September we bought ten guest post placements for this site and split them into two arms, decided before anything was ordered and published in the protocol at the time. For five, we submitted the host page for indexing ourselves through our own pipeline. For the other five we did nothing at all and left it to the publisher's own crawl rate. Same shelf, same week, same buyer.
What happened
| arm | placements | host page indexed | still not indexed |
|---|---|---|---|
| we submitted the host page | 5 | 5 | 0 |
| we left it alone | 5 | 3 | 2 |
Delivered to indexed, in hours, where it happened:
| id | arm | hours |
|---|---|---|
| P11 | submitted | 3.0 |
| P03 | submitted | 6.0 |
| P08 | submitted | 6.2 |
| P02 | submitted | 6.7 |
| P01 | submitted | 9.3 |
| P04 | left alone | 5.7 |
| P07 | left alone | 268.0 |
| P05 | left alone | 491.0 |
Of the five we left alone, one was indexed in under six hours, one took eleven days and one took twenty. The other two, P06 and P10, are still not in Google's index at day 26 and day 23.
The caveat that matters, stated before anyone finds it
P01 is contaminated and we are not counting it as evidence. Its host page appeared in Google about a minute after our submission, roughly nine hours after the article went live, which is too fast to attribute to us. It was almost certainly indexed on the publisher's own gravity and our submission happened to land at the same moment. That leaves four clean submitted placements, all indexed within seven hours.
Four against five is a small sample. It is not a study. It is what ten purchases on one site in one week can tell you, published because nobody else publishes it.
Why an unindexed link does nothing
Google's index is the set of pages it has decided to keep. Links are found by crawling pages and are counted from pages in the index. A page that has been published but not indexed is, for ranking purposes, a page Google has looked at and set aside. The link on it is real, a human can click it, and it is not yet part of anything Google is using to rank your site.
This is the same distinction we write about constantly and it applies to links exactly as it applies to your own pages. Indexed is admission. Ranking is a separate question, later, and dependent on other things.
The practical consequence for anyone buying links: the invoice is paid on publication, and publication is not the thing you were buying.
What we do not know yet
Whether any of this moved our rankings. We have not measured that and we will not guess at it. The 30-day checkpoint runs from 27 September, with a 90-day checkpoint on 26 November, both pre-registered: is the link still live, still dofollow, is the anchor intact, is the host page indexed, and what happened to the target page in Search Console. Those results will be published whatever they say.
We also do not know whether the two unindexed control pages will be indexed eventually. One of them has since done so at day twenty, which suggests slow crawl rates rather than a refusal. Publishers differ enormously in how often Google revisits them, and a buyer has no way to see that from a metrics table.
What to do with this if you are buying links
Ask whether the placement page is indexed, not just whether the article is live. They are different questions and only one of them matters.
Check it yourself rather than taking a report's word for it. Search Google for the exact URL with "site:" in front of it, or use any free index checker. Our own is the free index checker and answers one URL at a time with a reason when the answer is no.
Give it time before complaining, but not forever. Of the five we left alone, one took eleven days and one took twenty. A week of patience is reasonable. Three weeks of silence is a conversation with the publisher.
And if a vendor tells you indexing is not their problem, note that on five of our ten, doing something about it took the page from not indexed to indexed within seven hours.
What this proves, and what it does not
It shows that on ten placements bought from a screened shelf in one week, the host pages we submitted were indexed quickly and consistently, while the five we left alone took anywhere from six hours to never, so far, with two still out at more than three weeks.
It does not show that the links have helped us, that they will, or that this ratio holds on a bigger sample or on other sites. It is one buyer, one week, one site, published with the caveat about P01 in the open rather than buried. Every row is in the public pilot log at https://rank.fast/data/pilot-log.json , including the three placements that went wrong before delivery.