MultipleTokensMatched exception when using standard TokenCache

We have a client and service application where the client sends a token Bearer

and we use this token on the service side to get AccessToken

for other services like an endpoint Graph

. We are using the default TokenCache obtained using AuthenticationContext. We are facing a AdalException(AdalError.MultipleTokensMatched)

server side issue . My question is:

1) The code is still in prototype and no one else is using the client or service besides me, how can I end up here?

2) What exactly does TokenCache

not mean ThreadSafe

, and are there any better TokenCache

service-side implementations that I can use rather than build from scratch and test.

{"multiple_matching_tokens_detected: The cache contains multiple matching tokens. Call AcquireToken, again providing more requirements (eg UserId)"}