He attended the Tavrida National University in Simferopol and graduated in 2004 in the field of political science.

After graduating from university, Kostynskyi stayed in Simferopol and worked as an editor for a number of local newspapers and private companies.

[1] After the beginning of the Russian occupation of Crimea in early 2014, Kostynskyi left the peninsula for mainland Ukraine and started to work as a freelance columnist for the Ukrainian branch of Radio Free Europe/Radio Liberty.

[2] On 14 September 2015, President Petro Poroshenko appointed Kostynskyi as a member of the National Television and Radio Broadcasting Council of Ukraine.

[4] Following the start of Russia's full-scale invasion of Ukraine in 2022, Kostynskyi and other journalists and political activists from Crimea like Pavlo Kazarin, Volodymyr Balukh, Oleksandr Liev and Ismail Ramazanov joined the ranks of the Armed Forces of Ukraine and took part in the Defence of Kyiv.