I'm not to defend Heka, as I don't use it, but those "design flaws" only concerned development, not operations. If you read the message you quote, you would see

I'm not to defend Heka, as I don't use it, but those "design flaws" only concerned development, not operations. If you read the message you quote, you would see that Mozilla is still using it. And I take it you have measured Fluentd's performance, so you say so from experience, not flail around the typical opinion about language that can safely be attached to Java as well?