London Olympics bronze medallist Saina, who had reached the quarterfinals of previous editions in 2009 and 2011, brushed aside Olga 21-5 21-4 in just 23 minutes to set up a clash with 15th seed Thai Porntip Buranaprasertsuk in the prequarterfinals tomorrow.
Saina has a 5-0 record against Porntip but the Indian will have to be on guard as past records do not count and such matches could turn out to be tricky sometimes.
Both Saina and Sindhu had got a bye in the first round.
Seeded 10th, Sindhu, who won the Malaysia Grand Prix in May this year, had to sweat it out for an hour and 11 minutes before she could prevail over unseeded Imabeppu 21-19 19-21 21-17.
World number 12 Sindhu, who made her debut at the World Championships today, will next take on the winner of the match between second seed Wang Yihan of China and Indonesian Belaetrix Manuputi in the next round.