How can you optimize APM costs using retention filters?

Start from the fact that ingestion and indexing are billed differently: sampling controls how much is generated/ingested at all, while retention filters control what stays searchable for the 15-day window - the default Intelligent Retention Filter already keeps errors and a diverse latency sample without configuration, and its spans don't count against indexed-span billing.

Layer deliberate custom retention filters on top only for traces you specifically need guaranteed, complete visibility into beyond what intelligent sampling would naturally catch - for example, 100% retention on a small set of business-critical endpoints (checkout, payment) rather than broadly indexing everything.

Avoid the common mistake of creating many overlapping custom filters that all capture largely the same traffic; each additional filter adds to indexed volume independently, so redundant filters compound cost without adding proportional value - periodically reviewing filter overlap against actual query patterns keeps this in check.

Combine this with tuned ingestion sampling for very high-volume, low-value traffic (like health checks) so the base ingested volume itself stays lean, rather than relying on retention filters alone to control cost after the fact - the two levers work best used together, not as substitutes for each other.