Datadog Open Source Software Engineer interview questions

1) Recruiter reached out to me via GitHub, where he had found my email address after noticing my contributions to a variety of open-source projects, and told me they are searching for “individuals interested in writing open source code that will instrument thousands of PHP applications around the world”, and whether I would be interested in finding out more. 2) We agreed on a quick 30-minute hangout where the recruiter then told me a bit more about the role and explained the process. 3) As the recruiters feedback from the chat was positive, another hangout was organized with a software engineer who had already been working with DataDog for about a year. In the hangout, we first chatted a bit, then went on to do two coding challenges on Coderpad. The software engineer sent me problems, which I solved while talking about how I would do it. 4) As the software engineers feedback from the coding challenge was positive, I was then asked to share a couple of projects I was proud of. I forwarded a couple of open-source projects, along with blog posts I had written for them. In the meanwhile I also contributed a bit to Datadog’s open-source projects. 5) As the feedback from the reviewers was positive, I was then asked to work on a coding challenge homework. The task was to create an HTTP log monitoring program which should basically tail an HTTP log file and render a view in the console with interesting statistics, and which should update every 10 seconds. They suggested that quality submissions for this work take between 4 and 8 hours. 6) Since the feedback from the reviewers was positive, the recruiter asked me to propose dates for the final interview step, which would be a visit to Datadog's Paris office, to meet and talk to other developers and managers. I proposed a few dates. 7) The recruiter took a couple of days to reply. He then told me that he had had a meeting with his hiring manager and that the hiring manager had had concerns whether I “have the kind of understanding of PHP internals and low-level PHP that the role will require”. When I inquired what the hiring manager meant by that, the recruiter replied with something “the role will also leverage understanding the PHP engine itself which will require experience with and understanding of C”. That was the first time it was mentioned they were looking for someone who would be able to maintain PHP extensions. I replied that it would habe been respectful of my time if they had mentioned that earlier on in the process. The recruiter hasn’t replied since. Note: I consider myself an experienced software engineer, having built software for more than 25 years, and having worked with PHP for more than 18 years. At no time in the interview process exact requirements were shared with me.