This is a Game Dev Podcast with my guest Erick Passos from Photon Engine (Exit Games Inc.), a company that provides networking solutions and server architecture for online multiplayer games. I try to understand more about how how online multiplayer works in general and in particular how to use Photon's Quantum and Fusion to develop online games faster. Links to my Guest ➤ Photon Engine: https://www.photonengine.com/ Listen to the podcast on the go (Spotify, Apple Podcasts, etc.): ➤ https://tyrollerjonas.podbean.com/ 0:00 - Intro 0:17 - The 3 Layers of Multiplayer Tech 4:56 - Photon’s Products Across the Stack 6:54 - Transport Layers & Steam Relay Limitations 8:02 - Fusion vs Quantum + Designing for the Envelope 10:36 - Start from the Top: When Transport‑Only Makes Sense (MMOs, Server Logic) 15:53 - From PUN to Modern Netcode + Notable Games 21:21 - State Replication vs Determinism Explained 24:49 - Why Shooters Prefer Client‑Server (Lag Comp, Interest Mgmt) 26:11 - Server Build, Shared Mode, and Architecture Clarified 28:04 - Anti‑Cheat in Quantum: Replays, Spectators, Server Sim 31:49 - Grow Gradually: From Zero Servers to Full Validation 34:38 - Under the Hood: Predict‑Rollback, Physics, ECS, AI 38:32 - No Ring Buffer: Constant‑Time Rollbacks 45:28 - Testing Online, Tooling, and Community 46:15 - When to Use Fusion Instead of Quantum 50:29 - Performance: Verified vs Predicted, Clamps & Culling 52:34 - Bots, Matchmaking Math, and AI Costs 56:49 - AI Design: Verified‑Only Planning + Operational Prediction 58:02 - Verified‑Only Code Paths & Performance Targets 01:01:48 - Time Slicing AI for Stability 01:02:52 - RTS in Quantum: Flow Fields, Culling, and Use Cases 01:09:19 - Lockstep vs Prediction: Why He Avoids Lockstep 01:12:04 - Handling Rollback Spikes with Scheduling Tricks 01:13:05 - Auto‑Battlers: Verified‑Only + Snapshot Interpolation 01:15:29 - Hidden Info & Simultaneous Decisions; Server‑Gated Commands 01:21:35 - Using Quantum Offline? Licensing & Terms 01:25:03 - Determinism, ECS, and Quantum’s Hybrid Tables 01:29:22 - Could There Be a Deterministic Engine Built on Quantum? 01:31:08 - Cross‑Engine Experiments & Engine Integrations 01:35:42 - Open Worlds: Fusion Player‑Hosted vs Quantum 01:37:10 - Quantum for Open Worlds: Voxels, Persistence, NavMesh, Procgen 01:46:08 - Where Engines Stand on Multiplayer (Unreal, Unity, Source) 01:51:32 - Pricing: Free 100 CCU and Scaling Costs 01:54:45 - Long‑Tail Costs & Keeping Servers Alive 01:57:40 - Game Preservation: LAN, Offline, and Local Servers 02:04:48 - What’s New: Fusion 2.1, Quantum 3.1, Unreal Betas 02:05:55 - First Multiplayer? Start Small and Prototype 02:08:12 - Prototyping: Quantum vs Fusion (Shared Mode) 02:10:30 - From Prototype to Production: Managing Complexity 02:14:11 - What Makes a Multiplayer Hit? Trends vs Design 02:16:29 - Fusion’s New Physics Forecasting 02:17:47 - Riding vs Making Trends (Landfall’s Streak) 02:21:02 - Dogfooding: Prototyping to Improve the Tools 02:24:26 - Closing & Thanks My game "Thronefall": ➤ Steam: https://store.steampowered.com/app/2239150/Thronefall/ ➤ Discord: https://discord.gg/gVYctptyg8 ➤ Nintendo Switch: https://www.nintendo.com/en-gb/Games/Nintendo-Switch-download-software/Thronefall-2669627.html#Overview My game "Will You Snail": ➤ Play Will You Snail on Steam: https://store.steampowered.com/app/1115050/Will_You_Snail/ ➤ Join the Will You Snail Discord: https://discord.gg/G3mRDrK For the game developers among you: ➤ Join our creative game dev community on Discord: https://discord.gg/Ye6zzfQ