diff --git a/prisma/migrations/20260225122717_add_performance_indexes/migration.sql b/prisma/migrations/20260225122717_add_performance_indexes/migration.sql
new file mode 100644
index 0000000..b9a5759
--- /dev/null
+++ b/prisma/migrations/20260225122717_add_performance_indexes/migration.sql
@@ -0,0 +1,11 @@
+-- CreateIndex
+CREATE INDEX "AuditLog_evaluationId_idx" ON "AuditLog"("evaluationId");
+
+-- CreateIndex
+CREATE INDEX "Evaluation_evaluatorId_idx" ON "Evaluation"("evaluatorId");
+
+-- CreateIndex
+CREATE INDEX "Evaluation_templateId_idx" ON "Evaluation"("templateId");
+
+-- CreateIndex
+CREATE INDEX "EvaluationShare_userId_idx" ON "EvaluationShare"("userId");
diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index 837c1fe..03b92ca 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -66,6 +66,9 @@ model Evaluation {
   isPublic        Boolean  @default(false) // visible par tous (ex. démo)
   createdAt       DateTime @default(now())
   updatedAt       DateTime @updatedAt
+
+  @@index([evaluatorId])
+  @@index([templateId])
 }
 
 model EvaluationShare {
@@ -77,6 +80,7 @@ model EvaluationShare {
   createdAt    DateTime   @default(now())
 
   @@unique([evaluationId, userId])
+  @@index([userId])
 }
 
 model DimensionScore {
@@ -106,4 +110,6 @@ model AuditLog {
   newValue     String?
   userId       String?
   createdAt    DateTime @default(now())
+
+  @@index([evaluationId])
 }
diff --git a/src/actions/evaluations.ts b/src/actions/evaluations.ts
index 67dfac4..e67e974 100644
--- a/src/actions/evaluations.ts
+++ b/src/actions/evaluations.ts
@@ -72,11 +72,12 @@ export async function createEvaluation(data: {
       },
     });
 
-    for (const dim of template.dimensions) {
-      await prisma.dimensionScore.create({
-        data: { evaluationId: evaluation.id, dimensionId: dim.id },
-      });
-    }
+    await prisma.dimensionScore.createMany({
+      data: template.dimensions.map((dim) => ({
+        evaluationId: evaluation.id,
+        dimensionId: dim.id,
+      })),
+    });
 
     revalidatePath("/dashboard");
     return { success: true, data: { id: evaluation.id } };
@@ -177,30 +178,33 @@ export async function updateEvaluation(id: string, data: UpdateEvaluationInput):
     }
 
     if (dimensionScores && Array.isArray(dimensionScores)) {
-      for (const ds of dimensionScores) {
-        if (ds.dimensionId) {
-          await prisma.dimensionScore.upsert({
-            where: {
-              evaluationId_dimensionId: { evaluationId: id, dimensionId: ds.dimensionId },
-            },
-            update: {
-              score: ds.score,
-              justification: ds.justification,
-              examplesObserved: ds.examplesObserved,
-              confidence: ds.confidence,
-              candidateNotes: ds.candidateNotes,
-            },
-            create: {
-              evaluationId: id,
-              dimensionId: ds.dimensionId,
-              score: ds.score,
-              justification: ds.justification,
-              examplesObserved: ds.examplesObserved,
-              confidence: ds.confidence,
-              candidateNotes: ds.candidateNotes,
-            },
-          });
-        }
+      const validScores = dimensionScores.filter((ds) => ds.dimensionId);
+      if (validScores.length > 0) {
+        await prisma.$transaction(
+          validScores.map((ds) =>
+            prisma.dimensionScore.upsert({
+              where: {
+                evaluationId_dimensionId: { evaluationId: id, dimensionId: ds.dimensionId },
+              },
+              update: {
+                score: ds.score,
+                justification: ds.justification,
+                examplesObserved: ds.examplesObserved,
+                confidence: ds.confidence,
+                candidateNotes: ds.candidateNotes,
+              },
+              create: {
+                evaluationId: id,
+                dimensionId: ds.dimensionId,
+                score: ds.score,
+                justification: ds.justification,
+                examplesObserved: ds.examplesObserved,
+                confidence: ds.confidence,
+                candidateNotes: ds.candidateNotes,
+              },
+            })
+          )
+        );
       }
     }