SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3cb0fc98658f43c017222bc9bd25227f9aa426586f7db99e50958df9560a8316' 
  AND token = 'iVXmJoQmFM6Xv+LHRt6RlG+ez+PssGs/2yqfLUGbaPs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}