If you Google "good debt to equity ratio" one site says 2.0 - 2.5.
I'm not sure if this applies here.
Financial debt kills because free cash flow gets squeezed. For most tech companies, operating expenses constrain free cash flow.
Quick ratio [1] and free cash flow (or alternatively, operating cash flow) as a fraction of cash on hand (or less conservatively, current assets) would be my go-to acid tests.
The big caveat here is rising rates on floating rate debt, and the marginal response of revenue to higher rates.
Don't work for a tech company if you rely on wages for subsistence.
I used to work for the oil industry felt (and probably objectively is) far less stable.
Do employers even offer that kind of detailed information to employees?
And at a startup, particularly an early-stage one, I would feel pretty uncomfortable if they wouldn't tell me that information in an interview.