[PM-17562] Add in-memory cache for event integrations (#6085)

* [PM-17562] Add in-memory cache for event integrations

* Fix Sql error

* Fix failing test

* Add additional tests for new cache service

* PR suggestions addressed

src/Core/AdminConsole/Services/Implementations/EventIntegrations/EventIntegrationHandler.cs

@@ -14,7 +14,7 @@ public class EventIntegrationHandler<T>(
     IntegrationType integrationType,
     IEventIntegrationPublisher eventIntegrationPublisher,
     IIntegrationFilterService integrationFilterService,
-    IOrganizationIntegrationConfigurationRepository configurationRepository,
+    IIntegrationConfigurationDetailsCache configurationCache,
     IUserRepository userRepository,
     IOrganizationRepository organizationRepository,
     ILogger<EventIntegrationHandler<T>> logger)
@@ -27,7 +27,7 @@ public class EventIntegrationHandler<T>(
             return;
         }
 
-        var configurations = await configurationRepository.GetConfigurationDetailsAsync(
+        var configurations = configurationCache.GetConfigurationDetails(
             organizationId,
             integrationType,
             eventMessage.Type);

src/Core/AdminConsole/Services/Implementations/EventIntegrations/IntegrationConfigurationDetailsCacheService.cs

@@ -0,0 +1,73 @@
+using System.Diagnostics;
+using Bit.Core.Enums;
+using Bit.Core.Models.Data.Organizations;
+using Bit.Core.Repositories;
+using Bit.Core.Settings;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+namespace Bit.Core.Services;
+
+public class IntegrationConfigurationDetailsCacheService : BackgroundService, IIntegrationConfigurationDetailsCache
+{
+    private readonly record struct IntegrationCacheKey(Guid OrganizationId, IntegrationType IntegrationType, EventType EventType);
+    private readonly IOrganizationIntegrationConfigurationRepository _repository;
+    private readonly ILogger<IntegrationConfigurationDetailsCacheService> _logger;
+    private readonly TimeSpan _refreshInterval;
+    private Dictionary<IntegrationCacheKey, List<OrganizationIntegrationConfigurationDetails>> _cache = new();
+
+    public IntegrationConfigurationDetailsCacheService(
+        IOrganizationIntegrationConfigurationRepository repository,
+        GlobalSettings globalSettings,
+        ILogger<IntegrationConfigurationDetailsCacheService> logger
+    )
+    {
+        _repository = repository;
+        _logger = logger;
+        _refreshInterval = TimeSpan.FromMinutes(globalSettings.EventLogging.IntegrationCacheRefreshIntervalMinutes);
+    }
+
+    public List<OrganizationIntegrationConfigurationDetails> GetConfigurationDetails(
+        Guid organizationId,
+        IntegrationType integrationType,
+        EventType eventType)
+    {
+        var key = new IntegrationCacheKey(organizationId, integrationType, eventType);
+        return _cache.TryGetValue(key, out var value)
+            ? value
+            : new List<OrganizationIntegrationConfigurationDetails>();
+    }
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        await RefreshAsync();
+
+        var timer = new PeriodicTimer(_refreshInterval);
+        while (await timer.WaitForNextTickAsync(stoppingToken))
+        {
+            await RefreshAsync();
+        }
+    }
+
+    internal async Task RefreshAsync()
+    {
+        var stopwatch = Stopwatch.StartNew();
+        try
+        {
+            var newCache = (await _repository.GetAllConfigurationDetailsAsync())
+                .GroupBy(x => new IntegrationCacheKey(x.OrganizationId, x.IntegrationType, x.EventType))
+                .ToDictionary(g => g.Key, g => g.ToList());
+            _cache = newCache;
+
+            stopwatch.Stop();
+            _logger.LogInformation(
+                "[IntegrationConfigurationDetailsCacheService] Refreshed successfully: {Count} entries in {Duration}ms",
+                newCache.Count,
+                stopwatch.Elapsed.TotalMilliseconds);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError("[IntegrationConfigurationDetailsCacheService] Refresh failed: {ex}", ex);
+        }
+    }
+}

src/Core/AdminConsole/Services/Implementations/EventIntegrations/README.md

@@ -290,6 +290,35 @@ graph TD
     C1 -->|Has many| B1_2[IntegrationFilterRule]
     C1 -->|Can contain| C2[IntegrationFilterGroup...]
 ```
+## Caching
+
+To reduce database load and improve performance, integration configurations are cached in-memory as a Dictionary
+with a periodic load of all configurations. Without caching, each incoming `EventMessage` would trigger a database
+query to retrieve the relevant `OrganizationIntegrationConfigurationDetails`.
+
+By loading all configurations into memory on a fixed interval, we ensure:
+
+- Consistent performance for reads.
+- Reduced database pressure.
+- Predictable refresh timing, independent of event activity.
+
+### Architecture / Design
+
+- The cache is read-only for consumers. It is only updated in bulk by a background refresh process.
+- The cache is fully replaced on each refresh to avoid locking or partial state.
+- Reads return a `List<OrganizationIntegrationConfigurationDetails>` for a given key or an empty list if no
+  match exists.
+- Failures or delays in the loading process do not affect the existing cache state. The cache will continue serving
+  the last known good state until the update replaces the whole cache.
+
+### Background Refresh
+
+A hosted service (`IntegrationConfigurationDetailsCacheService`) runs in the background and:
+
+- Loads all configuration records at application startup.
+- Refreshes the cache on a configurable interval.
+- Logs timing and entry count on success.
+- Logs exceptions on failure without disrupting application flow.
 
 # Building a new integration