SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c0ac65040f318e0b33999212d5c667783c09d314d23b4d786e6087d7b12317df' 
  AND token = '6vOwTHGZ7BWxURKYHMkjuMfoake2wISxiTG9SsnKgj8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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