The 900-ton class Project 21631 Buyan-M is an stretched version of the 500-ton Buyan class gunboat. The Buyan-M features a larger and more sophisticated weapons payload including state-of-the-art missile systems. The 74-meter long ship is intended to perform anti-surface warfare (ASW) combat missions with secondary air defense capability thanks to Igla-1M surface-to-air missiles (SAM). The Buyan-M weapon system consists of a single A-190 100mm cannon, and AK-630-2 Duet air defense gun system, eight Club-S Kalibr anti-ship missiles, and Igla-1M SAMs mounted on a two 3M47 Gibka launcher. Besides, these ships are equipped with a 2 14.5mm machine guns. The ship is powered by a twin screw combined diesel and diesel (CODAD) propulsion system.

The ship’s main purpose is to protect Russia’s offshore economic zones and engage enemy warships along littoral areas. But not only. With a relatively small size, the ship stands out for its capability to strike at targets deep into enemy territory. It was instrumental in launching the first Kalibr SS-N-30A cruise missiles in October 7, 2015 from the Caspian Sea to strike terrorist targets in Syria.

The design incorporates stealth features to reduce the radar cross section. The flexible open architecture of the ships allows for modifications according to the future requirements. The corvette features better sea-keeping capabilities for navigation in stormy conditions. It can use weapons in conditions of sea state 4.

Missile Corvette Zeleny Dol was laid down 29 August 2012 at the Shipyard named after A.M.Gorky, Zelenodolsk (yard No.634), launched 2015, commissioned 13 November 2015.

The corvette served in the 166th Novorossiysk division of small missile ships of the 41st brigade of missile boats, based on Sevastopol.

In October 2016 the ship was transferred to the Baltic Fleet.