SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'adcf374061ab6f9d75f53c75437fe1af99e537f11ff1cbd64e6ef5fc1d6fdfaf' 
  AND token = 'VU4WbZnQwyokady+Vgpn5QDVvBLPTHKxcsRbtcEf7uE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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