SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df8b532b18d9ff323c314856a58995a55b3f31b6070d52b323a40ce94513de61' 
  AND token = 'AZOF6sgdRI/n9TsxG3GmkaFVsaswTjRVhdK+Nwb9YSQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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