Reliability, Effects, and Retries

using System;
using System.Collections.Generic;

var ledger = new Dictionary<(string Actor, string Key), int>();
int total = 0;
int first = Apply("actor-a", "operation-7", 10);
int replay = Apply("actor-a", "operation-7", 10);
int conflict = Apply("actor-a", "operation-7", 15);
Console.WriteLine($"first={first} replay={replay} conflict={conflict} total={total}");

int Apply(string actor, string key, int amount)
{
    if (ledger.TryGetValue((actor, key), out int existing)) return existing == amount ? 200 : 409;
    ledger[(actor, key)] = amount;
    total += amount;
    return 201;
}

first=201 replay=200 conflict=409 total=10

The first effect adds ten, replay adds nothing, and changed payload conflicts; no persistence or concurrency guarantee is tested.

using System;

int attempts = 3, attemptMilliseconds = 1000, backoffMilliseconds = 500, budgetMilliseconds = 3000;
int modeled = checked(attempts * attemptMilliseconds + (attempts - 1) * backoffMilliseconds);
Console.WriteLine($"worstMs={modeled} budgetMs={budgetMilliseconds} fits={modeled <= budgetMilliseconds}");

worstMs=4000 budgetMs=3000 fits=False

Three attempts plus two backoffs require 4000ms in the model, exceeding 3000ms; no operation waits or retries.