SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '75b95d3037742b5fd512dee03b3a396092bf878e9f6b1b3aabcc97d49fde342a' 
  AND token = 'pLvA7JngiDC/iBmPyI9iQH/ju5oZczqQsEwSTA0BNTI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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