[csomar]

The OP claims he did the implementation (so he was the software engineer too?):

> I designed and implemented most of the tools that are keeping it running so I think I’m qualified to talk about it.

[cmckn]

I read this as they built the “tools” (automation, orchestration, monitoring, etc.) for this system, not the system itself; which aligns with the common definition of SRE.

[mapme]

SRE is a mix of both. The expectation is you are able to write and understand any code the team is responsible for.