SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8635c3fb2f2d4f36570a37a3e8624eba43504db014468d6a1ed724b33c458be6' 
  AND token = 'MClt8IrlB4Y4aRuURntv1nUSy1L00qmlagPr26/iwlg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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