It was an unusual Sunday for 30-year-old Jake Yi, who stood with his team in the middle of a Mumbai trading floor as the screens flashed red.

The team had assembled for a special trading session to mark India's budget day, and they watched as stock prices tumbled in response to a new securities transaction tax. Yi, the head of India index options at IMC Trading BV, used the selloff as a teaching moment for the firm's crop of young traders — talking through spreads and risk in real time. These were the moments that mattered most: When volatility stripped away theory and forced decisions. For a young trader, there was no better classroom than a sharp market turn.