diff --git a/crates/common/migrations/012_build_metrics.sql b/crates/common/migrations/012_build_metrics.sql
new file mode 100644
index 0000000..b9ca6a3
--- /dev/null
+++ b/crates/common/migrations/012_build_metrics.sql
@@ -0,0 +1,45 @@
+-- Migration: Add build metrics collection
+-- Stores timing, size, and performance metrics for builds
+
+-- Create build_metrics table
+CREATE TABLE build_metrics (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    build_id UUID NOT NULL REFERENCES builds(id) ON DELETE CASCADE,
+    metric_name VARCHAR(100) NOT NULL,
+    metric_value DOUBLE PRECISION NOT NULL,
+    unit VARCHAR(50) NOT NULL,
+    collected_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW()
+);
+
+-- Index for efficient lookups by build
+CREATE INDEX idx_build_metrics_build_id ON build_metrics(build_id);
+
+-- Index for time-based queries (alerting)
+CREATE INDEX idx_build_metrics_collected_at ON build_metrics(collected_at);
+
+-- Index for metric name filtering
+CREATE INDEX idx_build_metrics_name ON build_metrics(metric_name);
+
+-- Prevent duplicate metrics for same build+name
+ALTER TABLE build_metrics ADD CONSTRAINT unique_build_metric_name UNIQUE (build_id, metric_name);
+
+-- Create view for aggregate build statistics
+CREATE VIEW build_metrics_summary AS
+SELECT
+    b.id as build_id,
+    b.job_name,
+    b.status,
+    b.system,
+    e.jobset_id,
+    j.project_id,
+    b.started_at,
+    b.completed_at,
+    EXTRACT(EPOCH FROM (b.completed_at - b.started_at)) as duration_seconds,
+    MAX(CASE WHEN bm.metric_name = 'output_size_bytes' THEN bm.metric_value END) as output_size_bytes,
+    MAX(CASE WHEN bm.metric_name = 'peak_memory_bytes' THEN bm.metric_value END) as peak_memory_bytes,
+    MAX(CASE WHEN bm.metric_name = 'nar_size_bytes' THEN bm.metric_value END) as nar_size_bytes
+FROM builds b
+JOIN evaluations e ON b.evaluation_id = e.id
+JOIN jobsets j ON e.jobset_id = j.id
+LEFT JOIN build_metrics bm ON b.id = bm.build_id
+GROUP BY b.id, b.job_name, b.status, b.system, e.jobset_id, j.project_id, b.started_at, b.completed_at;
diff --git a/crates/common/src/models.rs b/crates/common/src/models.rs
index 45e73ed..bb62ff8 100644
--- a/crates/common/src/models.rs
+++ b/crates/common/src/models.rs
@@ -164,6 +164,26 @@ pub struct BuildDependency {
   pub dependency_build_id: Uuid,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize, FromRow)]
+pub struct BuildMetric {
+  pub id:           Uuid,
+  pub build_id:     Uuid,
+  pub metric_name:  String,
+  pub metric_value: f64,
+  pub unit:         String,
+  pub collected_at: DateTime<Utc>,
+}
+
+pub mod metric_names {
+  pub const BUILD_DURATION_SECONDS: &str = "build_duration_seconds";
+  pub const OUTPUT_SIZE_BYTES: &str = "output_size_bytes";
+}
+
+pub mod metric_units {
+  pub const SECONDS: &str = "seconds";
+  pub const BYTES: &str = "bytes";
+}
+
 /// Active jobset view — enabled jobsets joined with project info.
 #[derive(Debug, Clone, Serialize, Deserialize, FromRow)]
 pub struct ActiveJobset {
diff --git a/crates/common/src/repo/build_metrics.rs b/crates/common/src/repo/build_metrics.rs
new file mode 100644
index 0000000..3f0d5b3
--- /dev/null
+++ b/crates/common/src/repo/build_metrics.rs
@@ -0,0 +1,60 @@
+use sqlx::PgPool;
+use uuid::Uuid;
+
+use crate::{
+  error::{CiError, Result},
+  models::BuildMetric,
+};
+
+pub async fn upsert(
+  pool: &PgPool,
+  build_id: Uuid,
+  metric_name: &str,
+  metric_value: f64,
+  unit: &str,
+) -> Result<BuildMetric> {
+  sqlx::query_as::<_, BuildMetric>(
+    "INSERT INTO build_metrics (build_id, metric_name, metric_value, unit) \
+     VALUES ($1, $2, $3, $4) ON CONFLICT (build_id, metric_name) DO UPDATE \
+     SET metric_value = EXCLUDED.metric_value, collected_at = NOW() RETURNING \
+     *",
+  )
+  .bind(build_id)
+  .bind(metric_name)
+  .bind(metric_value)
+  .bind(unit)
+  .fetch_one(pool)
+  .await
+  .map_err(CiError::Database)
+}
+
+pub async fn calculate_failure_rate(
+  pool: &PgPool,
+  project_id: Option<Uuid>,
+  jobset_id: Option<Uuid>,
+  window_minutes: i64,
+) -> Result<f64> {
+  let rows: Vec<(Uuid, String)> = sqlx::query_as(
+    "SELECT b.id, b.status::text FROM builds b JOIN evaluations e ON \
+     b.evaluation_id = e.id JOIN jobsets j ON e.jobset_id = j.id WHERE \
+     ($1::uuid IS NULL OR j.project_id = $1) AND ($2::uuid IS NULL OR j.id = \
+     $2) AND b.completed_at > NOW() - (INTERVAL '1 minute' * $3) ORDER BY \
+     b.completed_at DESC",
+  )
+  .bind(project_id)
+  .bind(jobset_id)
+  .bind(window_minutes)
+  .fetch_all(pool)
+  .await
+  .map_err(CiError::Database)?;
+
+  if rows.is_empty() {
+    return Ok(0.0);
+  }
+
+  let failed_count = rows
+    .iter()
+    .filter(|(_, status)| *status == "Failed")
+    .count();
+  Ok((failed_count as f64) / (rows.len() as f64) * 100.0)
+}
diff --git a/crates/common/src/repo/mod.rs b/crates/common/src/repo/mod.rs
index 7fc1109..cb41557 100644
--- a/crates/common/src/repo/mod.rs
+++ b/crates/common/src/repo/mod.rs
@@ -1,5 +1,6 @@
 pub mod api_keys;
 pub mod build_dependencies;
+pub mod build_metrics;
 pub mod build_products;
 pub mod build_steps;
 pub mod builds;