Hedging & Fallback Strategies for Tail Latency Reduction

1Concept

Hedging dispatches duplicate concurrent requests if the primary request takes longer than expected (e.g. p99 > 200ms), taking the result from whichever completes first to eliminate tail latency spikes.

2Architecture Diagram

Primary Request Dispatched
       │ (Takes > 150ms)
       ├──> Hedged Duplicate Request Dispatched to Replica Server 2
       │
Whichever finishes first wins; the slower request is cancelled!

3Code Example

using System;

public class HedgingConceptDemo
{
    public static void Main()
    {
        Console.WriteLine("Polly Hedging Strategy reduces p99 tail latency in financial & search APIs.");
    }
}

4Expected Output

Polly Hedging Strategy reduces p99 tail latency in financial & search APIs.

5Key Takeaways

• ✓Hedging dramatically reduces p99 and p99.9 latency spikes.
• ✓Only use hedging for idempotent read operations (e.g. GET/search).
• ✓Configure timeout thresholds carefully to prevent server load spikes.