Anyone pushed the BEAM for real-time simulation workloads? I built a multiplayer game server framework pushing 10,000 Entities @ 30Hz

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I’ve been building an open-source multiplayer game server framework in Elixir, and I wanted to share the results.

The Challenge: Can the BEAM handle MMO-scale real-time simulation? The conventional wisdom says “use C++ for game servers.” I wanted to prove otherwise.

The Results:

Metric Target Achieved
Tick time (10K entities) < 29ms 8ms avg, 13ms max
P99 tick time < 29ms 11.1ms
Bytes per entity < 20 18 (template bitpacking)
Per-player bandwidth < 1 MB/s 264 KB/s
Full broadcast bandwidth < 100 MB/s 5.2 MB/s
Crash recovery < 100ms 4.6ms

Key Techniques:

  • Bucket-parallel tick loop — Chunk entities across schedulers, not Task-per-entity

  • Fused encoding — Tick + serialize in one pass while data is hot in L1 cache

  • :maps.from_list — 9x faster than Map.put in a reduce (TIL!)

  • IO lists everywhere — Never concatenate binaries, let writev gather fragments

  • Time-travel debugging — Circular buffer with structural sharing for replay

  • Cross-zone shadows — PubSub-based visibility across zone boundaries

  • Async persistence — Snapshot + journal with atomic writes

The “aha moment”: Killing the 68ms sequential serialization bottleneck. Fused parallel encoding brought it down to 2ms for a typical player’s visible area (500 entities).

Architecture highlights:

  • Hybrid entity model (players as processes, NPCs as data in zone state)

  • ETS spatial grid for O(1) neighbor queries

  • Binary protocol with reliable_seq gap detection

  • Dead reckoning for shadow entity interpolation

  • Hysteresis on zone boundaries to prevent oscillation

Test suite: 340 tests, 0 failures

Still early days, but the engine handles the “10K goblin stress test” without breaking a sweat. Next up: TypeScript client SDK and a simple LiveView visualizer.

Curious if others have pushed the BEAM for real-time simulation workloads. What’s your experience?

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Hey, this is interesting as I didn’t see too many benchmarks of beam for performance, but what exactly is being tested here? I can see the metrics but don’t exactly understand the test scenario.
Is it like simulation of ‘10k players in the area’? If so then how many actions are they taking on each tick? I’ve read the comment 3 times and don’t see that info.
It’s interesting how scaling of that solution could look like (I mean how changes/effort would you have to make to have 10k simulations of 10k entities) and how much could you delegate to Zig/Rust if need be.