If you're in trouble and cannot find an answer to a question which goes beyond Stack Overflow...
If you have a not-so-usual solution for your problems but need to justify it to your boss...
If you like to think on your own rather than blindly follow "common wisdom" and "profound truth"...
...then 'No Bugs' Hare on Soft.ware might be the right place for you.
Your mileage may vary. Batteries not included

TBH, I am a big fan of actor- and reactor-like programming patterns (also known as Finite State Machines. While you’re not strictly required to use reactors and might be able to get away without them – they DO provide several very substantial benefits.

(Re)Actors, page 2:

On Zero-Side-Effect Interactive Programming, Actors, and FSMs

Abstract: “WHY are functional programming languages not popular for interactive programming purposes?” and “WHAT we can do about it?”
Quote: “IMNSHO, deterministic Actors are the very best thing in existence for interactive programming, with lots of very practical benefits (from production post-mortem, to protection of in-memory state against server faults).”
[]

Unity 5 vs UE4 vs Photon vs DIY for MMO

Quote: “You can still use HLAPI despite its shortcomings”
Another Quote: “If you’re using one of the engines above (and not your own one), and your game requires Client-Driven Development Flow, you may want to start with a single-player Unity 5, or with a single-player UE4.”
[]

Asynchronous Processing for Finite State Machines/Actors: from plain event processing to Futures (with OO and Lambda Call Pyramids in between)

Quote: “With ‘callback pyramid’ it is not easy to express the concept of ‘wait for more than one thing to complete’ , which leads to unnecessary sequencing, adding to latencies (which may or may not be a problem for your purposes, but still a thing to keep in mind).”
Another Quote: “Don’t even think of converting all of your code to a so-called Continuation-Passing-Style”
[]

Chapter VI(b). Server-Side Architecture. Front-End Servers and Client-Side Random Load Balancing

Quote: “[about Round-Robin DNS] one of these returned IPs can get cached by a Big Fat DNS server, and then get distributed to many thousands of clients”
Another Quote: “As a rule of thumb, Front-End Servers are a Good Thing™”
[]

Chapter VI(a). Server-Side MMO Architecture. Naïve, Web-Based, and Classical Deployment Architectures

Quote: “If you disrupt the game-event-currently-in-progress for more than 0.5-2 minutes, for almost-any synchronous multi-player game you won’t be able to get the same players back, and will need to rollback the game event anyway.”
Another Quote: “However, keep in mind, that all fall-tolerant solutions are complicated, costly, and for the games realm I generally consider them as an over-engineering (even by my standards).”
[]

Chapter V(d). Modular Architecture: Client-Side. Client Architecture Diagram, Threads, and Game Loop

Quote: “To have a good concurrency model, it is not strictly necessary to program in Erlang”
Another Quote: “Most of developers agree that FSM-based programming is beneficial in the medium- to long-run.”
[]

Chapter V(c). Modular Architecture: Client-Side. On Debugging Distributed Systems, Deterministic Logic, and Finite State Machines

Quote: “After your logic has failed in production, you can “replay” this inputs-log on your functionally identical in-house system, and the bug will be reproduced at the very same point where it has originally happened.”
Another Quote: “You can implement your Finite State Machine as a deterministic variation of a usual event-driven program”
[]