SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51e33b1cf506cea9df0ca7697e5447bdbc69df4c711db97b7e36b896a0922c9a' 
  AND token = 'IHjTSz83phmjAczbGLei4Y9wXERZEQCrgqz6pCPi1T4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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