Strangler paths fail less on technology and more on unfinished ownership. Teams introduce a gateway route or dual-publish bridge with good intentions, then leave the exit date unspoken. Months later the bridge is architecture, and nobody remembers who can retire it.
Before the first parallel path lands, write the lag threshold, mismatch rate, and calendar date when the old route retires if metrics stay green. Instrument both sinks with the same business key so comparisons are mechanical. Shadow traffic can prove readiness without exposing every user to the new path.
When metrics hold for the agreed window, close the bridge in the same release train that would otherwise keep extending it. Document why the window ended so the next extraction copies the habit instead of inventing a forever-temporary path.
