SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8517452380872462b5342201fa2ad85fcecacebc56adcba9c8db64376c4bf341' 
  AND token = '0ZuNDzrs1MaD1ZqzE4X4R7cI9u/7Q0l43OJEBMDiCmc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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