Watch out, this affects small rails applications with few dynos as well.

If you hit the wall with one dyno and add another one, you won't get twice the throughput even though you pay twice the price.

I've always had suspicions about this on some smaller apps but never really looked into it. You can configure New Relic to measure round-trip response times on the client side. At peak loads those would be unreasonably high. Much higher than can be explained by huge latencies even.