Low-level
adjective
Relatively unimportant
“The low-level bureaucrat couldn't help us and his boss could have but wouldn't.”
Not intense
“The low-level radiation released won't kill you immediately, but avoid long term exposure.”
Of, or relating to a program, or to code in which each statement corresponds to a single machine instruction
“The assembler generates low-level code.”
Synonyms: at the coal face, brass tacks, details, front line, nitty-gritty, nuts and bolts, trenches