Build a template engine: {{user.name}} from nested dicts, then conditionals, then loops
A three-level build that quietly tests whether your L1 design survives L3. Regex substitution wins level one and loses the round; here's the token-based structure that carries through conditionals and loops.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
A three-level build that quietly tests whether your L1 design survives L3. Regex substitution wins level one and loses the round; here's the token-based structure that carries through conditionals and loops.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
