Tech Lead interview question · Most asked
How do you decide how much process a technical decision needs?
Summary
By how costly it is to reverse. Reversible 'two-way door' decisions should be made quickly by the people doing the work; hard-to-reverse 'one-way door' decisions get a design doc, alternatives, review and an ADR.
Longer Answer
Ask: what would it cost to undo this in six months? A CI tool or internal library is cheap to switch; a primary data store, public API contract or data model with migrations isn't. Make one-way doors more reversible where cheap (abstractions, flags, versioned APIs, dual writes). Amazon's 2016 shareholder letter describes reversible decisions as two-way doors that "can use a light-weight process", and suggests most decisions should be made with around 70% of the information you'd like.
Key Points
- Classify by reversibility first
- Fast for two-way doors, rigorous for one-way doors
- Make irreversible choices more reversible
Deep dive: Decision Speed: One-Way and Two-Way Doors
Explanation
What interviewers look for
Matching process to risk, and awareness that slow decisions also have a cost.
Red flags
- One heavy process for everything
- Quick, unreviewed choices of data stores or public APIs
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