Start with an inventory, not a platform
Startups rarely lack tools for secrets. They lack certainty about where secrets currently live. Before adopting anything fancy, spend one hour listing every credential your team relies on and where copies exist: cloud consoles, git repos, laptops, chat threads, and that one spreadsheet nobody admits to.
The inventory alone usually surfaces urgent problems, like a production token committed years ago or shared in an onboarding document that has been forwarded five times.
Build three simple habits
First, keep secrets out of source control using environment files that are git-ignored and a scanning hook that catches mistakes. Second, centralize runtime secrets in whatever managed store your cloud already provides rather than inventing a homegrown scheme.
Third, fix the human path. Most leaks at small companies happen during handoff, not storage. Give the team one standard way to send a credential: encrypt it in the browser, share a link that expires, done. Habits beat platforms when the team is five people and shipping fast.