UiPath Caching

Multilayer caching for .NET — L1 in-memory + L2 Redis, cross-node sync over Redis Streams, single-flight stampede protection, hydrating cache, and CloudEvents — behind a small, opinionated DI surface.

The library powers caching in UiPath Platform services. It is built for multi-tenant workloads that need a hot in-process tier, a shared Redis tier, and cross-node coherence — without each service reinventing the same patterns.

Quick Start

dotnet add package UiPath.Caching
dotnet add package UiPath.Caching.Polly
dotnet add package UiPath.Caching.CloudEvents

Wire it once in Program.cs:

using UiPath.Caching;
using UiPath.Caching.CloudEvents;
using UiPath.Caching.Config;
using UiPath.Caching.Polly;

var section = builder.Configuration.GetSection("Caching");
builder.Services.AddCaching(
    section,
    b => b.AddRedisConnection().AddBroadcast()
          .AddRedis().AddInMemoryRedis().AddMemory()
          .AddResilienceStrategies().AddCloudEvents(),
    o => { section.Bind(o); o.AppShortName = "my-service"; });

Inject and call:

public class UserService(ICache<User> cache, IUserRepository repo)
{
    public ValueTask<User?> GetAsync(int id, CancellationToken ct) =>
        cache.GetOrAddAsync(id.ToString(), c => repo.LoadAsync(id, c),
                            TimeSpan.FromMinutes(5), ct);
}

Minimum appsettings.json:

{
  "Caching": {
    "AppShortName": "my-service",
    "Connections": {
      "Redis": { "ConnectionString": "localhost:6379" }
    }
  }
}

That's it. Everything else has a sensible default. Five-minute onboarding lives in docs/quickstart.md; the full settings reference is in docs/reference/settings.md.

Features

Resiliency

• Single-flight stampede protection — one factory runs per key on a cache miss; other callers coalesce. In-process via ILocalLock (default on); cross-node via IDistributedLock (AddInMemoryRedis() registers the impl automatically — opt in with DistributedLockEnabled: true; AddMemory()-only or custom wiring needs an explicit .AddRedisDistributedLock()).
• Hydrating cache — proactive background refresh before a key expires (CachePolicy.RehydrateEnabled + RehydrateOptions). Avoids the expiry-miss path on hot keys so reads against still-live entries don't pay the factory cost. First-time misses still run the factory on the foreground caller.
• Polly pipelines — retry + circuit-breaker around every cache op (AddResilienceStrategies). Configurable per-op timeout, break duration, and rethrow behavior.
• Connection-aware L1 fallback — UseLocalOnlyWhenDisconnected + LocalMaxExpirationDisconnected keep the cache useful when Redis blips.

Distribution

• Multilayer L1 + L2 — in-process MemoryCache + Redis, written together, read L1-first. Different TTLs per tier.
• Redis Streams backplane — durable, at-least-once cross-node L1 invalidation with consumer groups and replay. Fallback to Pub/Sub if you don't need durability.
• Per-topic options — fine-grained overrides for fan-out, polling, backpressure, and the streams notify doorbell.
• Sharded Pub/Sub doorbell (Redis 7+) — NotifyEnabled + NotifyShardedPubSub drop publish-to-deliver latency from PollInterval to network RTT without leaving the shard.
• Redis Cluster aware — shard-key routing, master/replica split (writes to master, reads from replicas).

Advanced

• IHashCache<T> — one entry, many fields, one TTL. Subset reads via HMGET; side-channel metadata via HashCacheEntryOptions. Bundled GET + TTL in a single transaction for hydrating-cache math.
• Named cache policies — per-ICache<T> settings keyed by typeof(T).FullName (TTLs, jitter, rehydration, lock profile). Inherits from DefaultCachePolicy with null-means-inherit semantics.
• L2 jitter — JitterMaxDuration spreads cluster-wide expirations after bulk writes.
• Large-value auditing — AuditEnabled + LargeValueThreshold log writes over a byte threshold.

Observability

• ICachingTelemetryProvider seam with span-based tag bags (allocation-free when telemetry is off). An OpenTelemetry adapter (ActivitySource + Meter) ships as UiPath.Caching.OpenTelemetry; OpenTelemetry Redis instrumentation wires up via the IConnectionMultiplexerFactory hook (see the sample).
• CloudEvents — broadcast events wrapped in the CNCF CloudEvents envelope (UiPath.Caching.CloudEvents).

Architecture

flowchart LR
    App["App code\n(ICache<T> / IHashCache<T>)"] --> ML[MultilayerCache]
    ML -->|read first| L1[(L1: in-process)]
    ML -->|miss / write| L2[(L2: Redis)]
    ML -. wraps .-> SF[Single-flight\nlock]
    ML -. wraps .-> POL[Polly pipeline]
    L2 -.write fan-out.-> TOPIC{{Redis Streams\nbackplane}}
    TOPIC -->|invalidation event| OtherL1[(Other nodes' L1)]
    OtherL1 -.evicts.-> ML2[MultilayerCache on node B]

Loading

InMemoryRedis is the default provider — multilayer with the backplane wired. Redis (L2-only) and InMemory (L1-only, optional broadcast) are available for single-tier scenarios. See docs/concepts.md for the full mental model.

Packages

Package	When you need it
UiPath.Caching.Abstractions	Always (transitive).
UiPath.Caching	Always — providers, topics, locks.
UiPath.Caching.Polly	Resilience pipelines. Recommended.
UiPath.Caching.CloudEvents	CloudEvents envelope for broadcast events. Recommended.
UiPath.Caching.Queue	Redis set ("queue") support — ISetCache / AddRedisSetCache.

Documentation

Topic	Doc
5-minute onboarding	docs/quickstart.md
Architecture & mental model	docs/concepts.md
Resilience (single-flight, hydrating, jitter, Polly)	docs/how-to/resilience.md
Broadcast (per-topic, notify doorbell, sharded Pub/Sub)	docs/how-to/broadcast.md
Hash cache (metadata, bundled GET+TTL)	docs/how-to/hash-cache.md
Telemetry + custom strategies	docs/how-to/telemetry-and-strategies.md
Short copy-paste patterns	docs/recipes/
Settings reference (every option, every default)	docs/reference/settings.md
Public interface surface	docs/reference/interfaces.md
Glossary	docs/reference/glossary.md
Sample app (Aspire AppHost)	docs/sample-app.md
Changelog	CHANGELOG.md

Requirements

• .NET — 8.0 and 10.0.
• Redis — 6.0+. Redis 7.0+ required for sharded Pub/Sub (SPUBLISH/SSUBSCRIBE) on the streams notify doorbell.
• StackExchange.Redis — pulled transitively; no direct dependency needed in consumers.

License

MIT.