I think the point of the article is that adding an index to a big table with lots of writes is practically not possible: Quoting from the article: real prob

I think the point of the article is that adding an index to a big table with lots of writes is practically not possible: Quoting from the article: real problem for big tables as adding a few columns to our biggest tables started to take 2+ hours or sometimes was completely unpredictable and exceeded our announced downtime windows. Apparently, adding a column was even a problem during a maintenance window because the runtime was even longer than they expected. Compared to PostgreSQL: As long as the new column is NULL and does not have a default value, it’s in practice a no-op to add it. No matter if your table size is 100MB or 100GB