How would you reduce cheating in an online game?

What the interviewer wants to hear

• Server authority: never trust the client
• Validate inputs and movement on the server
• Send clients only the information they need
• Client-side anti-cheat and integrity checks as an extra layer
• Detection with analytics, reports and delayed bans
• Secure economy and APIs

Model answer

The most important rule is to never trust the client. The server owns important state like health, inventory, currency and match results, and clients only send inputs. The server validates those inputs, for example checking movement speed, fire rate and line of sight, so speed hacks and teleport hacks fail. To limit wallhacks, the server avoids sending positions of enemies the player cannot possibly see or hear. Client-side anti-cheat and code integrity checks add another layer against aimbots and memory editing, but they can be bypassed, so they are not the main defence. I would also use analytics and player reports to spot unusual statistics, and ban in waves so cheat makers learn less. Store and economy APIs need the same server-side checks to prevent duplication exploits.

More hard Game Developer questions

• How would you design the networking for a fast-paced online multiplayer shooter?
• Design a flexible ability and buff system for an RPG with hundreds of skills.
• How do you manage memory in a large game that ships on consoles with fixed memory?
• Explain how a modern real-time rendering pipeline draws a frame, and where the common performance costs are.
• The game averages 60 FPS but players complain about hitches every few seconds. How do you find and fix them?
• How would you build a replay system that lets players rewatch a match, and what makes it hard?
• How would you architect world streaming for a large open-world game?
• How do you use multiple CPU cores in a game without race conditions and with real speed-ups?
• How would you design the backend for an online game with matchmaking and dedicated servers?