In a Go Lambda with multiple clients (AWS SDK, MongoDB, Cognito, EventBridge), segregate the sync.Once values by real usage path — never one initAll() that ties every client together. Each dependency you instantiate during INIT (init() or eager globals) is paid at every cold start, on every code path; the happy path must not pay the cold-start tax for clients it never touches. Use when a Go Lambda has 2+ clients across branches, when you see init() opening a Mongo/DB connection unconditionally, or when adding a new client to an existing handler. (Go has no SnapStart, so this matters more than in Java/Python.)
