SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a20b97f1ed151c4e102797f0e4e940a14651530241f83a8253ddfbe1a9181f03' 
  AND token = 'kDjUiGcyJxo/gdS+NgiQIkfRA2+0VUwa4TbK1zXhnJo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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