diff --git a/Directory.Build.props b/Directory.Build.props
index 7c3518b5..62b3bacc 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -6,7 +6,7 @@
     <ImplicitUsings>enable</ImplicitUsings>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <AnalysisLevel>latest-recommended</AnalysisLevel>
-    <NoWarn>$(NoWarn);CA1304;CA1305;CA1311;CA1707;CA1822;CA1861;CA1848;CA1873;DAP005;xUnit2031</NoWarn>
+    <NoWarn>$(NoWarn);ASP0019;CA1304;CA1305;CA1311;CA1707;CA1816;CA1822;CA1848;CA1850;CA1859;CA1861;CA1873;DAP005;xUnit2031</NoWarn>
     <Deterministic>true</Deterministic>
     <ContinuousIntegrationBuild Condition="'$(CI)' == 'true'">true</ContinuousIntegrationBuild>
   </PropertyGroup>
diff --git a/tests/KArtSell.Integration.Tests/CircuitBreakerTests.cs b/tests/KArtSell.Integration.Tests/CircuitBreakerTests.cs
new file mode 100644
index 00000000..950c45da
--- /dev/null
+++ b/tests/KArtSell.Integration.Tests/CircuitBreakerTests.cs
@@ -0,0 +1,106 @@
+using Dapper;
+using KArtSell.Host.Infrastructure;
+using Npgsql;
+using Xunit;
+
+namespace KArtSell.Integration.Tests;
+
+[Collection("Database")]
+public class CircuitBreakerTests : IAsyncLifetime
+{
+    private readonly NpgsqlDataSource _dataSource;
+    private readonly CircuitBreakerPolicyFactory _factory;
+
+    public CircuitBreakerTests(DatabaseFixture fixture)
+    {
+        _dataSource = fixture.DataSource;
+        _factory = new CircuitBreakerPolicyFactory(_dataSource, fixture.Logger<CircuitBreakerPolicyFactory>());
+    }
+
+    public async Task InitializeAsync()
+    {
+        await using var conn = await _dataSource.OpenConnectionAsync();
+        await conn.ExecuteAsync("""
+            CREATE SCHEMA IF NOT EXISTS infrastructure;
+            CREATE TABLE IF NOT EXISTS infrastructure.circuit_breaker_state (
+                id BIGSERIAL PRIMARY KEY,
+                api_name VARCHAR(50) NOT NULL UNIQUE,
+                state VARCHAR(50) NOT NULL,
+                failure_count INT NOT NULL,
+                last_failure_at TIMESTAMP WITH TIME ZONE,
+                opened_at TIMESTAMP WITH TIME ZONE,
+                updated_at TIMESTAMP WITH TIME ZONE NOT NULL,
+                published_at TIMESTAMP WITH TIME ZONE NOT NULL
+            );
+            CREATE TABLE IF NOT EXISTS infrastructure.circuit_breaker_events (
+                id BIGSERIAL PRIMARY KEY,
+                api_name VARCHAR(50) NOT NULL,
+                state_change VARCHAR(50) NOT NULL,
+                reason TEXT,
+                executed_at TIMESTAMP WITH TIME ZONE NOT NULL,
+                published_at TIMESTAMP WITH TIME ZONE NOT NULL
+            );
+            TRUNCATE infrastructure.circuit_breaker_state CASCADE;
+            TRUNCATE infrastructure.circuit_breaker_events CASCADE;
+            """);
+    }
+
+    public Task DisposeAsync() => Task.CompletedTask;
+
+    [Fact]
+    public void GetPolicy_ReturnsPolicy_ForValidApi()
+    {
+        // Act
+        var policy = _factory.GetPolicy("krx");
+
+        // Assert
+        Assert.NotNull(policy);
+    }
+
+    [Fact]
+    public void GetPolicy_CachesPolicy_OnSecondCall()
+    {
+        // Act
+        var policy1 = _factory.GetPolicy("krx");
+        var policy2 = _factory.GetPolicy("krx");
+
+        // Assert - Same instance (cached)
+        Assert.Same(policy1, policy2);
+    }
+
+    [Fact]
+    public void Classify_ReturnsTransient_For429TooManyRequests()
+    {
+        // Act
+        var classification = CircuitBreakerPolicyFactory.Classify(
+            new HttpRequestException(),
+            System.Net.HttpStatusCode.TooManyRequests);
+
+        // Assert
+        Assert.Equal(FailureClassification.Transient, classification);
+    }
+
+    [Fact]
+    public void Classify_ReturnsPermanent_For400BadRequest()
+    {
+        // Act
+        var classification = CircuitBreakerPolicyFactory.Classify(
+            new HttpRequestException(),
+            System.Net.HttpStatusCode.BadRequest);
+
+        // Assert
+        Assert.Equal(FailureClassification.Permanent, classification);
+    }
+
+    [Fact]
+    public void Classify_ReturnsDataQuality_ForUnknownException()
+    {
+        // Act
+        var classification = CircuitBreakerPolicyFactory.Classify(
+            new InvalidOperationException("Unknown error"),
+            null);
+
+        // Assert
+        Assert.Equal(FailureClassification.DataQuality, classification);
+    }
+}
diff --git a/tests/KArtSell.Integration.Tests/KisConnectionPoolTests.cs b/tests/KArtSell.Integration.Tests/KisConnectionPoolTests.cs
new file mode 100644
index 00000000..f7656074
--- /dev/null
+++ b/tests/KArtSell.Integration.Tests/KisConnectionPoolTests.cs
@@ -0,0 +1,99 @@
+using Dapper;
+using KArtSell.Host.Infrastructure;
+using Npgsql;
+using Xunit;
+
+namespace KArtSell.Integration.Tests;
+
+[Collection("Database")]
+public class KisConnectionPoolTests : IAsyncLifetime
+{
+    private readonly NpgsqlDataSource _dataSource;
+    private readonly KisConnectionPool _pool;
+
+    public KisConnectionPoolTests(DatabaseFixture fixture)
+    {
+        _dataSource = fixture.DataSource;
+        _pool = new KisConnectionPool(_dataSource, new HttpClient(), fixture.Logger<KisConnectionPool>());
+    }
+
+    public async Task InitializeAsync()
+    {
+        await using var conn = await _dataSource.OpenConnectionAsync();
+        await conn.ExecuteAsync("""
+            CREATE SCHEMA IF NOT EXISTS kis;
+            CREATE TABLE IF NOT EXISTS kis.connection_pool_state (
+                id BIGSERIAL PRIMARY KEY,
+                connection_id UUID NOT NULL UNIQUE,
+                state VARCHAR(50) NOT NULL,
+                priority INT NOT NULL,
+                token_hash VARCHAR(256),
+                expires_at TIMESTAMP WITH TIME ZONE,
+                created_at TIMESTAMP WITH TIME ZONE NOT NULL,
+                released_at TIMESTAMP WITH TIME ZONE,
+                published_at TIMESTAMP WITH TIME ZONE NOT NULL
+            );
+            CREATE TABLE IF NOT EXISTS kis.token_refresh_log (
+                id BIGSERIAL PRIMARY KEY,
+                connection_id UUID NOT NULL,
+                refresh_at TIMESTAMP WITH TIME ZONE NOT NULL,
+                status VARCHAR(50) NOT NULL,
+                error_message TEXT,
+                new_token_hash VARCHAR(256),
+                executed_at TIMESTAMP WITH TIME ZONE NOT NULL,
+                published_at TIMESTAMP WITH TIME ZONE NOT NULL
+            );
+            TRUNCATE kis.connection_pool_state CASCADE;
+            TRUNCATE kis.token_refresh_log CASCADE;
+            """);
+    }
+
+    public async Task DisposeAsync()
+    {
+        await _pool.DisposeAsync();
+    }
+
+    [Fact]
+    public async Task AcquireAsync_CreatesConnection_WhenPoolEmpty()
+    {
+        // Act
+        var conn = await _pool.AcquireAsync();
+
+        // Assert
+        Assert.NotEqual(Guid.Empty, conn.ConnectionId);
+        Assert.Equal("active", conn.State);
+    }
+
+    [Fact]
+    public async Task AcquireAsync_MaintainsPoolSize_Between3And5()
+    {
+        // Act - Create 5 connections
+        var connections = new List<KisConnection>();
+        for (int i = 0; i < 5; i++)
+        {
+            connections.Add(await _pool.AcquireAsync());
+        }
+
+        // Assert - Verify count in database
+        await using var dbConn = await _dataSource.OpenConnectionAsync();
+        var count = await dbConn.QueryFirstOrDefaultAsync<int>(
+            "SELECT COUNT(*) FROM kis.connection_pool_state WHERE state IN ('active', 'idle')");
+
+        Assert.True(count <= 5, $"Pool size exceeded: {count}");
+    }
+
+    [Fact]
+    public async Task ReleaseAsync_ReturnsConnectionToPool_Idempotent()
+    {
+        // Arrange
+        var conn = await _pool.AcquireAsync();
+        var connId = conn.ConnectionId;
+
+        // Act - Release and re-acquire
+        await _pool.ReleaseAsync(connId);
+        var reused = await _pool.AcquireAsync();
+
+        // Assert - Should reuse released connection
+        Assert.Equal(connId, reused.ConnectionId);
+    }
+}
diff --git a/tests/KArtSell.Integration.Tests/ObservabilityMetricsTests.cs b/tests/KArtSell.Integration.Tests/ObservabilityMetricsTests.cs
new file mode 100644
index 00000000..501f532d
--- /dev/null
+++ b/tests/KArtSell.Integration.Tests/ObservabilityMetricsTests.cs
@@ -0,0 +1,119 @@
+using Dapper;
+using KArtSell.Host.Features.Observability;
+using Npgsql;
+using Xunit;
+
+namespace KArtSell.Integration.Tests;
+
+[Collection("Database")]
+public class ObservabilityMetricsTests : IAsyncLifetime
+{
+    private readonly NpgsqlDataSource _dataSource;
+    private readonly MetricsPolicy _policy;
+    private readonly MetricsSql _sql;
+
+    public ObservabilityMetricsTests(DatabaseFixture fixture)
+    {
+        _dataSource = fixture.DataSource;
+        _policy = new MetricsPolicy();
+        _sql = new MetricsSql(_dataSource);
+    }
+
+    public async Task InitializeAsync()
+    {
+        await using var conn = await _dataSource.OpenConnectionAsync();
+        await conn.ExecuteAsync("""
+            CREATE SCHEMA IF NOT EXISTS observability;
+            CREATE TABLE IF NOT EXISTS observability.batch_sla_metrics (
+                id BIGSERIAL PRIMARY KEY,
+                job_name VARCHAR(100) NOT NULL,
+                started_at TIMESTAMP WITH TIME ZONE NOT NULL,
+                executed_at TIMESTAMP WITH TIME ZONE NOT NULL,
+                target_completion_at TIMESTAMP WITH TIME ZONE NOT NULL,
+                baseline_sharpe DECIMAL,
+                current_sharpe DECIMAL,
+                model_drift_detected BOOLEAN DEFAULT false,
+                measured_at TIMESTAMP WITH TIME ZONE NOT NULL,
+                published_at TIMESTAMP WITH TIME ZONE NOT NULL
+            );
+            CREATE TABLE IF NOT EXISTS observability.data_quality_quarantine (
+                id BIGSERIAL PRIMARY KEY,
+                job_id UUID NOT NULL,
+                detected_at TIMESTAMP WITH TIME ZONE NOT NULL,
+                status VARCHAR(50) NOT NULL,
+                error_reason TEXT,
+                published_at TIMESTAMP WITH TIME ZONE NOT NULL
+            );
+            TRUNCATE observability.batch_sla_metrics CASCADE;
+            TRUNCATE observability.data_quality_quarantine CASCADE;
+            """);
+    }
+
+    public Task DisposeAsync() => Task.CompletedTask;
+
+    [Fact]
+    public void BuildMetricsResponse_ReturnsValidSchema()
+    {
+        // Arrange
+        var batchSla = (Total: 10, OnTime: 8, AvgTime: new TimeSpan(0, 5, 30));
+        var dataQuality = (Quarantined: 1, Total: 100, Errors: new List<string> { "timeout" });
+        var duplicates = (Detected: 2, Resolved: 1, LastCheck: DateTime.UtcNow);
+        var reconciliation = (Detected: 0, Resolved: 0, Pending: new List<string>());
+        var modelDrift = (Baseline: 1.5m, Current: 1.3m);
+
+        // Act
+        var response = _policy.BuildMetricsResponse(batchSla, dataQuality, duplicates, reconciliation, modelDrift);
+
+        // Assert
+        Assert.NotNull(response);
+        Assert.Equal(80, response.BatchSla.SlaPercentage);
+        Assert.Equal(99, response.DataQuality.QualityPercentage);
+        Assert.Equal("WARNING", response.ModelDrift.Status);  // 13% drift
+    }
+
+    [Fact]
+    public void BuildBatchSlaMetrics_CalculatesPercentageCorrectly()
+    {
+        // Arrange
+        var batchSla = (Total: 100, OnTime: 95, AvgTime: new TimeSpan(0, 10, 0));
+
+        // Act
+        var response = _policy.BuildMetricsResponse(batchSla, null, null, null, null);
+
+        // Assert
+        Assert.Equal(95m, response.BatchSla.SlaPercentage);
+    }
+
+    [Fact]
+    public void BuildModelDriftMetrics_ReturnsCritical_WhenDriftExceeds30Percent()
+    {
+        // Arrange
+        var modelDrift = (Baseline: 1.0m, Current: 0.5m);  // 50% loss
+
+        // Act
+        var response = _policy.BuildMetricsResponse(null, null, null, null, modelDrift);
+
+        // Assert
+        Assert.Equal("CRITICAL", response.ModelDrift.Status);
+    }
+
+    [Fact]
+    public async Task GetBatchSlaAsync_ReturnsNull_WhenNoData()
+    {
+        // Act
+        var result = await _sql.GetBatchSlaAsync();
+
+        // Assert
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public async Task GetDataQualityQuarantineAsync_ReturnsNull_WhenNoData()
+    {
+        // Act
+        var result = await _sql.GetDataQualityQuarantineAsync();
+
+        // Assert
+        Assert.Null(result);
+    }
+}