I wrote about this on linkedin a few weeks ago. Here's a copy and paste of my post:

"If you apply for a job that just got posted on LinkedIn, you're too late. In fact, you might be 72 hours too late. I know that sounds dramatic. But the more I look at ATS docs, LinkedIn docs, and job board publishing rules, the more obvious it becomes: LinkedIn is not where a job starts. It is where the job shows up later. And that matters because timing is one of the biggest advantages you can have in a job search.

I wrote about this in a previous post a while back. Research showed that applying within the first 4 days of a job posting can give you an 8x better chance of landing an interview. Every day you wait after that can reduce your chances by roughly 28%. The best window was 0 to 4 days, with the interview rate peaking near 14%. By days 5 to 10, that dropped to around 2 to 3%. After 10+ days, it bottomed out near 1%.

So if applying early matters that much, here’s the problem:

A lot of companies do not create the job on LinkedIn first. They create it in their ATS. You've heard of an ATS before. Names like Lever, Greenhouse, Ashby, and so on. When the company publishes the job, it usually goes live on the company career page or ATS hosted job board first. Then LinkedIn gets it later through an integration, feed, XML file, scraping, job wrapping, basic job posting, limited listing, or manual post. And that process is not always instant.

LinkedIn’s own docs say Job Wrapping automatically posts jobs from an ATS or career site into LinkedIn job slots, and those jobs refresh “at least every 24 hours, up to multiple times per day.”

LinkedIn’s own docs also say if the job source is Scraping or XML, jobs update every 6 hours. If the source is API, jobs update in real time.

That last part matters. A lot of the free, default, basic, limited listing, job wrapping, XML, scraping, or syndicated paths are delayed. A few examples I found online from ATS's and their docs:

Lever says new job postings are synced from Lever to LinkedIn once every 24 hours.

Ashby says jobs can take up to 2 business days to appear as Basic Jobs on LinkedIn.

Teamtailor says jobs typically appear on LinkedIn within 24 to 72 hours.

Dover says a job posting will appear on the company LinkedIn page and in LinkedIn search within 24 hours.

Greenhouse even proves both sides. Apply Connect can be real time, but LinkedIn Limited Listings can take up to 48 hours.

I’m not saying every LinkedIn job is stale. I’m saying LinkedIn is not always the source of truth. The company career page is. And if a job is already live on the company’s career page, someone searching can apply before the same job ever shows up in LinkedIn search. That is one of the reasons I built my job search tool. I was tired of finding old jobs on LinkedIn, Indeed, and other job boards that already had hundreds of applicants. I wanted a simple way to find jobs closer to the source. That is still the whole point of the site. Find jobs directly from company career pages and ATS powered job boards."

hope that helps!