All four Java services share one HS256 secret, so any service can mint platform tokens - accepted
debt for the single-instance phase. Move to RS256/EdDSA: only user-service holds the private key
and mints tokens; the gateway and services verify via a JWKS endpoint with caching. Ship as
auth/v2 in checkers-contracts with a rolling migration plan (verifiers accept both until the last
HS256 tokens expire).
All four Java services share one HS256 secret, so any service can mint platform tokens - accepted
debt for the single-instance phase. Move to RS256/EdDSA: only user-service holds the private key
and mints tokens; the gateway and services verify via a JWKS endpoint with caching. Ship as
auth/v2 in checkers-contracts with a rolling migration plan (verifiers accept both until the last
HS256 tokens expire).