What is Minecraft?
Minecraft is a sandbox video game developed by Mojang Studios and released in 2011. Players explore a procedurally generated three-dimensional world made entirely of blocks, gathering resources, crafting tools, building structures, and surviving against creatures that emerge at night. There is no single objective — the game adapts to however you want to play, whether that means constructing elaborate cities, mining deep underground, or battling the Ender Dragon.
Since its release, Minecraft has become one of the best-selling games of all time, with hundreds of millions of copies sold across virtually every platform: PC, consoles, and mobile. A large part of its appeal is multiplayer — the ability to share a world with friends. And this is where the architecture gets interesting.
The Client-Server Model
When most people think of playing Minecraft with others, they are thinking of the client-server model. In this architecture there is one central machine — the server — that holds the authoritative state of the world: every block, every mob, every item. Players connect to it as clients, sending inputs (move, mine, place block) and receiving back the current state of the world.
Running a local server
The simplest client-server setup is a LAN game. When you open a single-player world to the LAN in Minecraft, your own machine becomes the server and anyone on the same network can join. Your computer is doing two jobs at once: running your game client and running the server. This works fine for a small group of people in the same house, but it has clear limits — the world only exists while your machine is on, your IP address is not reachable from outside your network, and performance degrades as you add players.
You can go a step further by running a dedicated Minecraft server process on a machine you control (a spare PC, a VPS, a cloud VM). This separates the server from any individual player’s client, so the world persists even when everyone logs off. The architecture is still the same: one authoritative server, many clients.
Free hosting services: Aternos
Services like Aternos make the client-server model accessible without any infrastructure knowledge. Aternos provides free Minecraft server hosting — you create an account, pick a version and any mods you want, and they spin up a server for you. Your friends connect to it as clients exactly as they would to any other server.
The trade-off is resource constraints. Free tiers on services like Aternos typically put the server to sleep when no players are online, limit RAM, and may queue your startup behind other users. But the model is identical: one central server owns the world state, clients connect to it, all traffic flows through that single point.
This is the defining characteristic of client-server: a single authoritative node. If that node goes down, the service is unavailable.
Paid hosting services: Minecraft Realms
Minecraft Realms is Mojang’s official paid hosting service. For a monthly subscription fee, Mojang (now under Microsoft) manages and maintains a dedicated server for you. You get a persistent world that is always online, automatic backups, and a simple invitation system so friends can join without dealing with IP addresses or port forwarding.
Realms is deliberately simple — there are no mods on Bedrock Edition Realms (Java Edition supports a limited set of modpacks), no root access, and no configuration beyond the basics. The trade-off is convenience for control: you pay for a managed experience and get reliability in return.
Compared to Aternos, Realms costs money but removes the friction of queued startups, RAM limits, and idle timeouts. It is the natural next step for a group that has outgrown a free tier and wants a server that just works without any self-hosting overhead.
The Distributed Systems Model
Minecraft Realms is Mojang’s own subscription-based hosting product, and while it superficially looks like just “managed hosting,” it is backed by infrastructure that operates as a distributed system.
What makes it distributed?
A distributed system is a collection of independent computers that work together and appear to users as a single coherent system. No single machine is “the” server in an absolute sense. Work, state, and responsibility are spread across multiple nodes.
Realms is built on cloud infrastructure (Microsoft Azure, since Microsoft acquired Mojang in 2014). Behind the scenes, your Realm runs on hardware spread across data centers. Redundancy, failover, automatic restarts, and load balancing are all handled transparently. If the physical machine hosting your Realm fails, the system migrates your world and brings it back online on different hardware — you likely never notice.
Key properties of a distributed system that Realms exhibits:
- Fault tolerance — no single point of failure. Hardware can fail without the world being lost.
- Geographic distribution — infrastructure is replicated across regions, reducing latency for players in different locations.
- Transparent management — backups, updates, and scaling happen without operator intervention.
- Always-on availability — unlike Aternos, Realms worlds are accessible 24/7 without a warm-up queue.
The cost of distribution
Nothing is free. Realms is a paid subscription, and that cost pays for the engineering required to coordinate state across distributed nodes, replicate data, and maintain availability guarantees. Distributed systems are harder to build and operate than a single server — they must deal with network partitions, consistency trade-offs, and the complexity of coordinating machines that can fail independently.
For most small groups of friends, a single server (local, free-tier, or self-hosted) is entirely sufficient. Distributed infrastructure becomes worth the cost when you need reliability, scale, or geographic reach that a single machine cannot provide.
Summary
| Local / LAN | Aternos (free hosting) | Minecraft Realms | |
|---|---|---|---|
| Architecture | Client-server | Client-server | Distributed system |
| Who runs the server | You | Aternos | Microsoft/Mojang |
| Always online | No | No (sleeps when idle) | Yes |
| Fault tolerant | No | Partial | Yes |
| Cost | Free | Free (limited) | Paid subscription |
| Best for | LAN parties | Small friend groups | Reliable, always-on play |
Minecraft is a surprisingly clean lens for understanding these two architectural patterns. The game itself hasn’t changed — the block-breaking and building are identical. What changes is where the world lives and how that state is managed. A LAN game and a Realm are the same experience as a player, but represent fundamentally different ideas about how computers should work together.