We are currently doing transaction protection for betting service. The problem is there are certain moments when a transaction can be "chewed" by the system (for example, if you send your bet to the wallet generated for the previous betting round because you webpage was not refreshed in time - or you simply had the wrong address in the buffer) - to ensure that this will not going to happen we need to track every transaction made to the wallet associated with service and instantly (or within a small time frame) return it back to the user. The concept is fairly simple, however we found out that constant tracking eats a huge chunk of the server`s resource and we need further optimize code in order to avoid overloading when we will have significant amount of users made their bets. Those changes might be invisible from the outside, but absolutely crucial to ensure service stability and reliability.
Also, having coders on salary have its own downside - they tend to stop working on weekends.