SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c761c8ea4b71b3c72638356bee9393bbadf72c5545d2e1e8581d718e86b56529' 
  AND token = 'dSlgWPDpGnmvVMDgSq+Fa9Sjf1WprvIBgFxCcFtK/FQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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