AnyCable vs. Action Cable: A Benchmark War

„Our Rails app’s real-time features were crumbling under 10K users—until we switched WebSocket stacks. Here’s what exploded, what improved, and what caught fire.“

When your Action Cable infrastructure starts choking on traffic, the Rails community whispers one word: AnyCable. But does it actually deliver on its promises?

We benchmarked both under load, failure, and cost—here’s the raw, unfiltered truth.

1. The Contenders

Action Cable (Default Rails)

✅ Pros:

• Built into Rails
• Easy setup (rails g channel Chat)
• Good enough for small apps

❌ Cons:

• Redis bottlenecks at ~5K connections
• Memory leaks in long-running connections
• No horizontal scaling without hacks

AnyCable (The Challenger)

✅ Pros:

• 10x more connections (Go-based WebSocket server)
• Protocol-compatible with Action Cable
• Built-in gRPC support for scale

❌ Cons:

• Extra moving parts (Go server, NATS/Redis)
• Slightly harder to debug

2. The Benchmark Battleground

We tested 3 critical scenarios on AWS t3.xlarge instances:

Test 1: Connection Scalability

Verdict: AnyCable wins by 10x.

Test 2: Broadcast Latency

Sending 1K messages/second to 10K clients
| Metric | Action Cable | AnyCable |
|———————-|————-|———-|
| P95 latency | 840ms | 62ms |
| Messages lost | 17% | 0% |

Verdict: AnyCable’s gRPC backend avoids Redis pub/sub bottlenecks.

Test 3: Failure Recovery

Pulling the plug on the WebSocket server
| Metric | Action Cable | AnyCable |
|———————-|————-|———-|
| Auto-reconnect rate | 72% | 98% |
| Time to restore | 8.2s | 1.4s |

Verdict: AnyCable’s Go runtime handles TCP chaos better than Ruby.

3. The Hidden Costs

Infrastructure Complexity

graph TD
  A[Rails] -->|gRPC| B[AnyCable-Go]
  B -->|NATS| C[Redis]

Action Cable is just Rails → Redis. AnyCable adds two new services.

Debugging Nightmares

• Action Cable: Full Ruby stack traces
• AnyCable: Logs split between Go + Ruby

Pro tip: Use AnyCable-Go’s WebSocket inspector:

ANYCABLE_DEBUG=1 anycable-go

4. When to Switch

Stick with Action Cable If:

• You have <1K concurrent users
• Your team hates DevOps
• You’re not using Redis elsewhere

Switch to AnyCable If:

• You’re adding real-time to a monolith
• You need >5K connections
• You’re already using gRPC

5. Migration Guide

Step 1: Install AnyCable

# Gemfile
gem "anycable-rails", "~> 1.3"

Step 2: Configure gRPC

# config/anycable.yml
production:
  rpc_host: "127.0.0.1:50051"
  redis_url: "redis://localhost:6379/1"

Step 3: Deploy AnyCable-Go

docker run -p 8080:8080 anycable/anycable-go 
  --redis=redis://redis:6379/1 
  --rpc_host=anycable-ruby:50051

Full zero-downtime migration guide: anycable.io/docs

6. Surprising Findings

• HTTP/2 matters: AnyCable over h2 is 2.3x faster than HTTP/1.
• No need to rewrite channels: 100% protocol compatibility.
• Cold starts hurt: AnyCable-Go needs ~1GB RAM to be happy.

„But Our App Isn’t Discord!“

Neither was ours. You don’t need massive scale to benefit:

1. Start with one channel (e.g., NotificationsChannel)
2. Compare memory usage (you’ll likely see 60% less RAM)
3. Expand as you grow

Tried AnyCable? Share your benchmarks below!