You load 50 orders, then query items once per order = 51 queries. Fix with Include / projection. ShopNest invoice list uses .Include(o => o.Items) so one SQL round-trip returns orders + lines.
Infosys rounds often probe: Enterprise .NET.
Themes commonly reported in public MNC interview experiences (AmbitionBox / LinkedIn / Glassdoor-style). Practice aloud; keep answers this short in the real round.