SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a848a304de454de6675627f7cbdee8f590ce2c0ddeda841d87093b3559b82eb2' 
  AND token = '3P9GR46jmAPER99MdTdTQkgjnX+L3TeT1GgDo+mr0WY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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