SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fab38ec5e31464cc2bac4373b598fd1360e1f6dfe0a5c35a66a0891d3baa800' 
  AND token = 'IwyM118EmBknR3Wj5Ygbkfid33D0uXcPYbT5iGUtLY4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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