SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91ec6f18f1eeb3415ad53193e361d3ebb3de46379af0697a4148b46965644a74' 
  AND token = 'kpe8kPy2rHbFPCQm3/nPac+YPRrfMtQ64b0DYgY00pc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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