Twenty Seven Attempts

The call path is

client -> gateway -> orders -> inventory -> pricing

Each of the three server-to-server hops retries twice on failure, so up to 3 attempts per hop, with no coordination between layers. Steady user traffic is 500 requests per second.

pricing browns out and fails every call for 40 seconds. What load does pricing see, and what actually bounds it?

$3^4 = 81$ attempts, because the client retries the gateway on the same policy.

$3^3 = 27$ attempts per user request, so about $500 \times 27 = 13{,}500$ requests per second. A retry budget capping retries at 10 percent of each client's outbound traffic bounds amplification near $1.1^3 \approx 1.33$ , or roughly 665 per second.

$3 \times 3 = 9$ attempts per user request, so about 4,500 per second, since the three hops each add their own attempts on top of the original.

27 attempts and 13,500 per second, but exponential backoff with full jitter brings the offered load back to about 500 per second by spreading the retries out in time.