SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3f7ed55487de09c0dc1ee6b8e32799565b2dece06b66f9f784c98b943b2e257' 
  AND token = 'iACsNgAn6z0zHZY+6rYFdCBq5CwSlV68uMO8M/9njlg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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