SOP: Fallback depth — single backup vs multi-tier chain

SOP: Fallback depth — single backup vs multi-tier chain

Step 1 — Map failure modes per offer: paused, capped, geo-rejected, advertiser 5xx. Each needs a catch.
Step 2 — Start with a single house-offer backup. For low-volume campaigns, one safety net is enough — deeper chains add latency for no gain.
Step 3 — Go multi-tier only on high-volume geos:
☐ Tier 1: best EPC offer
☐ Tier 2: second-best, same geo/device
☐ Tier 3: broad house offer that accepts everything
Step 4 — Cap chain depth at 3. Each hop adds latency and a failure point; beyond 3 you're hiding a routing problem.
Step 5 — Alert on fallback rate. If Tier 1 sends >10% to fallback, that's a config or advertiser issue, not normal.

Tradeoff: deep chains maximize fill rate but add latency and obscure root causes.

Review fallback-hit rates daily; re-rank tiers weekly by EPC.