SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b751a7161179466ca68ea811eb9256ef4e411ff480f6b8aebf98d242cab5e38' 
  AND token = '8k/W9pZW9PMM7XeVtAHOkdau4n6OqX6vhPGmg+EhSkE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}