SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68cfe648a31402b405e6ca367b1983bee9a50e9c9265f05024a8a13214cce27d' 
  AND token = 'Svjgf40kNSnVMfw6ABiR4gVFFwIoHHsWiJRDYG/HhtM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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