Having successfully built (and sold!) a technology startup myself, I would always, always opt for a managed database service. Yes, it’s more expensive on paper and you want to run the numbers and choose the right offering. But nothing beats the peace of mind of storing your customers’ data on a system that others (Google Cloud in our case) look after. Not to mention that you’re better off focussing on your core value proposition and spending your scarce resources there than to have a database administrator on your payroll.
