The distinction between HOT/WARM and COLD purely exists to allow customers to choose the fastest disk they can afford to hold recent data, while using cheaper storage for long term data.
If you don't do that, you don't really need COLD.
Take a look here for some more detail.
Hey @daniel333, here's more info about buckets How "bucket spread" affects search performance
When you search for something in your indexed data, Splunk gives you the results of your search in reverse chronological order-- we assume you want information about what's happening most recently first, with older results arriving later. Splunk first looks in the hot bucket, then the warm buckets, then cold. The frozen db is never searched.
If you search for "fflanda" in your index, Splunk looks to see if it's in db-hot first. If it is, Splunk then looks at the timestamp of the event that "fflanda" was found in, and the range of time covered by db-hot. Based on that, Splunk decides whether to show you that result right away, or to look in the warm buckets to see if there are any more recent results than that. It will look in every warm bucket (and then in every cold one) that has a range that includes the timestamp of the event in whch "fflanda" was found.
In the case of the first example, the "standard" bucket setup, Splunk will immediately know that there are no results for "fflanda" that are more recent than the one it found in db-hot, and begin giving you your results immediately.
However, in the second example's case, Splunk will look in every warm bucket because it might contain a more recent result than right now--the "bucket span" extends to the future, so finding a more recent event than right now is possible. And Splunk will therefore wait to display any of your search results to you until it has finished searching every bucket that could yield such a result.
This is how the "spread" in time of the data in your buckets affects search performance. How you 'tune' your buckets can make a big difference to your search experience.