SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6cff272d08a1f713e1187018ab488144d94e10aa8ca3c21ba39a9c41ee5bb60d' 
  AND token = '/0uLX2nY1PVs07eu8GjLfMUA4I+tEMvsjXCRbqJ7uXg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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