It’s a bit of an unknown, since the service is a proprietary black box. With that being said, my guess:
A database with perceptual hash data for volumes and volumes of CSAM.
Means to generate new hashes from media
Infrastructure for adding and auditing more of it
REST API for hash comparisons and reporting
Integration for pushing reports to NCMEC and law enforcement.
None of those things are impossible or out of reach…but, collecting a new database of hashes is challenging. Where do you get it from? How is it stored? Do you allow the public to access the hash data correctly, or do you keep it secret like all the other solutions do?
I’m imagining a solution where servers aggregate all of this data up to a dispatch platform like the one described above, possibly run by a non-profit or NGO, which then dispatches the data to NCMEC directly.
The other thing to keep in mind is that solutions like photoDNA are HUGE. I’m talking like hundreds of thousands of pieces of reported media per year. It’s something that would require a lot of uptime, and the ability to handle a significantly high amount of requests on a daily basis.