https://heroesofthestorm.fandom.com/wiki/Boost
Boosts are consumable items that increases the amount of experience (for out-of-game Hero Level and Player Level progression) by an additional 100% and gold by 150% gold per match until they expire. A Boost's bonuses applied on end-of-game score screens for each match the user completes while the Boost is active.
Additionally, all players on a team will receive 5% bump in experience for each active Boost at the end of each match. That mean players can receive up to a 45% XP bonus if all 10 players in game have a Boost active. In addition to these stacking Boost XP buffs, you’ll also be able to retroactively Boost your Gold and XP gains at the end of a match by applying a Boost from the Score Screen.
A player is also notified of their active Boost’s remaining duration in the chat box upon logging into the game. The timer begins from the moment a Boost is purchased and continues in real time (not game time).
Players should keep in mind the following:
A Boost’s XP bonus will only affect a player's out-of-game Hero Level and Player Level progression, and has no effect on actual gameplay during a match.
Boost benefits are additive. This means the bonuses they provide are added to the base amount of XP or gold a player receives by playing a game.
A Boost's duration can last between one day and 360 days depending on what the player obtains as a reward or purchases. If a Boost is currently active, purchasing or receiving an addition Boost will extend the current duration. Boost are not paused or extended for maintenance downtime.