A Vendor Dependency Index is a measurement method used to estimate how hard it would be to replace a technology provider. It usually combines factors such as data portability, contract limits, integration depth, staff familiarity, process reliance, and the availability of alternative suppliers. The result is not a universal standard, but a practical way to turn vendor lock-in into a measurable risk.
In cyber security, the index matters because heavy dependence on one provider can slow incident response, recovery, and strategic change. If identity, backups, logging, or core workflows all depend on the same platform, an organization may have fewer options during outages, security failures, or price pressure. Defenders use the index in governance reviews, architecture planning, and exit strategy testing to identify weak points before they become operational traps. It helps teams answer a simple question: if this vendor stopped being available, how quickly could we move?