SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'da3ddba1cee924f861badf370c32d22887c8960ca265219219d1d5cb410b0142' 
  AND token = 'Tm2bxs/EISoQR0+fZzcqoK4eC6wR0axuLWcCMlHJVwg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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