SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8ac9ddabe437c906083fcd1905a243a213a7ec7d77306dc01eaf0e43b41b678' 
  AND token = '2SxpddNBdh36MZNeXh68vlDsXn+OuLy5BakeRQNMmgQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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