SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8e615f81bfad1f7fa8a80e687d50173862d285b3bd677b2a740c9c736d1b2476' 
  AND token = 'PqLLxHuqhNnjBIuJiNstxGI9AAPzgTHmJ+Lry5AAfwA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00056

JSON explain

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