SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b9a5249990e1ed46fade84080b800e281a174e612302b064aeadd8a79d10a3b' 
  AND token = '0/PSHsm5Y9XxvNoyokkCn8o93mebTYI8pwaIdCDQ/+o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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