NSE's trading engine was fine. The market still stopped for four hours.

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India's largest stock exchange stopped trading. For about four hours. And the trading engine? It was working fine.

NSE has telecom links from two providers. That morning, both report instability. On all their links. Trading still works. But the online risk system gets hit. 11:40 am. NSE halts trading in every segment. Rival BSE keeps running normally. NSE reopens at 3:45 pm.

Why stop a working engine? Because every trade gets a risk check. In real time, it makes sure nobody takes positions they can't cover. The links went unstable. And the risk system was hit. Without it, NSE said, the market could not continue normally.

But here's the catch. On paper, NSE had backups for all of it. Two providers? Both unstable, the same morning. A risk system in high availability mode? Still affected. A disaster recovery site, meant for exactly this? Trading never moved there.

The regulator, SEBI, asked why trading didn't move to the recovery site. It alleged they missed their own four-hour recovery target. June 2023: they settle. About 72 point 6 crore rupees. No admission, no denial.

Redundancy only helps if the backups don't fail together. A recovery site only helps if you've tested moving to it. And anything the main path can't run without? Protect it like the main path.

Full breakdown in the lecture.