SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4d885694832307908bb3fd880e5d63299a630be698e33ac0fbfe0438bb35cee' 
  AND token = '2xa8JvfWKm+hTP9LjPWSMzhUSgOCNoixZWeEvHeE9DQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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