Time to kill

Time to Kill (TTK) is a metric in gaming that measures how long it takes classes to kill one another. This is either an average (global TTK) or specific to a certain class (individual TTK) A high time to kill means that the time between the first shot fired and the death of a player is long, while low time to kill means that the time is short. Time to kill is generally relatively high in class shooters, allowing combatants more time to interact.

Time to kill is closely linked to damage per second.

High vs Low
Different time to kill rates have their own strengths and weaknesses, which give very different experiences and heavily affect how the game is played.

Low TTK
Low times mean that the person firing has a greater advantage, while the person being fired upon has much less time to react. This heavily favors tactical positioning, and works well for tactical shooters like Counter-Strike. The advantage is that players are encouraged to think ahead and give themselves as much advantage as possible. The major disadvantage is that players are much less likely to have time to react to being attacked. This is good for shooters with few mechanics at play, like arena shooters or tactical shooters. However, for class shooters, where counterplay between abilities is a key feature of the game, this is not ideal.

High TTK
Higher times give the person being attacked a greater chance to fight back. This favors quick reflexes and thinking while in combat, and can lead to visually exciting and stimulating battles. The advantage to high times to kill is that players are encouraged to take risks and fight their way out of situations. The disadvantage is that the element of surprise is much less effective in securing kills. This is preferable for class shooters, where each combatant has an arsenal of abilities and skills to use to counter their opponent. This time to kill slows the pacing of the game down and extends fights, making it less suited to tactical gameplay. Great care must be taken not to have a time to kill that is too high, though, as it might lead to the game feeling "spongey," with classes seemingly unaffected by incoming damage.

Affecting Time to Kill
Two of the "Big 4" mechanics directly affect time to kill: damage and health. The balance between these two mechanics directly affect how long it takes to kill a particular class. Their effect on time to kill is approximately equal, leaving the question of which tool to use at the discretion of the game maker.