Workflow Design and Optimization
Workflow design questions test whether you understand execution order and data flow. Alteryx runs tools when all upstream inputs are satisfied; tools on independent branches can run in parallel, but a single tool with multiple inputs waits for all of them. The Run Order and Tool Container settings (enabled/disabled) and the Detour tools (Detour and Detour End) control conditional execution - a disabled container's tools do not run and pass no data.
Key concepts: the Formula vs Multi-Row Formula vs Multi-Field Formula distinction; the role of Select for column order and type; and caching - Alteryx caches tool results so re-running only executes changed branches, which is why editing an early tool invalidates everything downstream. Questions often ask why a downstream tool shows a stale result: the answer is usually a cached upstream tool that must be re-run or the workflow refreshed.
Traps: confusing Union order (it follows input anchor order, not spatial position) and assuming Sort before a Sample guarantees stable top-N (it does, but only if the sort is upstream on the same branch). Also, Block Until Done is required when writing to the same file from multiple branches to prevent file-lock errors.
Rule of thumb: design left-to-right, keep one logical purpose per container, and use Block Until Done whenever two streams write to one output.
Worked example: two Summarize branches both write to output.xlsx. Running fails intermittently with a file-in-use error. Fix: insert a Block Until Done tool so the first Output Data completes before the second begins.