Do you have any reliable source for that claim? Because that Xitter account seems to contain almost exclusively anti-Muslim, anti-immigrant, pro-Trump, Qanon-leaning, conspiracy theory posts. It doesn't come across as a particularly believable source.
For instance, the claim that Fujitsu sub-contracted the Emergency Alert System to Infosys has already been debunked by multiple fact-checking sites.
Infosys did not work on emergency alerts system
I can't find anything relating to the claim that Infosys worked on the Horizon system, probably because it's such a recent addition to the earlier untrue social media claims about the Emergency Alert System.