diff --git a/backend/app/routers/threat_actors.py b/backend/app/routers/threat_actors.py
index b780ef1..733112a 100644
--- a/backend/app/routers/threat_actors.py
+++ b/backend/app/routers/threat_actors.py
@@ -7,28 +7,24 @@ threat actor profiles imported from MITRE CTI.
 import logging
 from typing import Optional
 
-from fastapi import APIRouter, Depends, HTTPException, Query
-from sqlalchemy import func, or_
-from sqlalchemy.orm import Session, joinedload
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy.orm import Session
 
 from app.database import get_db
 from app.dependencies.auth import get_current_user
 from app.models.user import User
-from app.models.threat_actor import ThreatActor, ThreatActorTechnique
-from app.models.technique import Technique
-from app.models.test import Test
-from app.models.test_template import TestTemplate
-from app.models.enums import TechniqueStatus
+from app.services.threat_actor_service import (
+    get_actor_coverage,
+    get_actor_detail,
+    get_actor_gaps,
+    list_actors,
+)
 
 logger = logging.getLogger(__name__)
 
 router = APIRouter(prefix="/threat-actors", tags=["threat-actors"])
 
 
-# ---------------------------------------------------------------------------
-# GET /threat-actors — Listado con filtros
-# ---------------------------------------------------------------------------
-
 @router.get("")
 def list_threat_actors(
     search: Optional[str] = Query(None),
@@ -45,92 +41,17 @@ def list_threat_actors(
 
     **Requires** authentication (any role).
     """
-    query = db.query(ThreatActor)
+    return list_actors(
+        db,
+        search=search,
+        country=country,
+        motivation=motivation,
+        sophistication=sophistication,
+        target_sectors=target_sectors,
+        offset=offset,
+        limit=limit,
+    )
 
-    # Filters
-    if search:
-        from app.utils import escape_like
-        pattern = f"%{escape_like(search)}%"
-        query = query.filter(
-            or_(
-                ThreatActor.name.ilike(pattern),
-                ThreatActor.description.ilike(pattern),
-                func.cast(ThreatActor.aliases, func.text()).ilike(pattern),
-            )
-        )
-
-    if country:
-        query = query.filter(ThreatActor.country == country)
-
-    if motivation:
-        query = query.filter(ThreatActor.motivation == motivation)
-
-    if sophistication:
-        query = query.filter(ThreatActor.sophistication == sophistication)
-
-    if target_sectors:
-        from app.utils import escape_like
-        # JSONB contains check
-        query = query.filter(
-            func.cast(ThreatActor.target_sectors, func.text()).ilike(f"%{escape_like(target_sectors)}%")
-        )
-
-    # Total count
-    total = query.count()
-
-    # Paginate
-    actors = query.order_by(ThreatActor.name).offset(offset).limit(limit).all()
-
-    # For each actor, count techniques and calculate basic coverage
-    results = []
-    for actor in actors:
-        tech_count = (
-            db.query(ThreatActorTechnique)
-            .filter(ThreatActorTechnique.threat_actor_id == actor.id)
-            .count()
-        )
-
-        # Quick coverage calculation
-        covered = (
-            db.query(ThreatActorTechnique)
-            .join(Technique, ThreatActorTechnique.technique_id == Technique.id)
-            .filter(ThreatActorTechnique.threat_actor_id == actor.id)
-            .filter(Technique.status_global.in_([
-                TechniqueStatus.validated,
-                TechniqueStatus.partial,
-            ]))
-            .count()
-        )
-
-        coverage_pct = round((covered / tech_count * 100), 1) if tech_count > 0 else 0.0
-
-        results.append({
-            "id": str(actor.id),
-            "mitre_id": actor.mitre_id,
-            "name": actor.name,
-            "aliases": actor.aliases or [],
-            "country": actor.country,
-            "target_sectors": actor.target_sectors or [],
-            "target_regions": actor.target_regions or [],
-            "motivation": actor.motivation,
-            "sophistication": actor.sophistication,
-            "mitre_url": actor.mitre_url,
-            "technique_count": tech_count,
-            "coverage_pct": coverage_pct,
-            "is_active": actor.is_active,
-        })
-
-    return {
-        "total": total,
-        "offset": offset,
-        "limit": limit,
-        "items": results,
-    }
-
-
-# ---------------------------------------------------------------------------
-# GET /threat-actors/{id} — Detalle
-# ---------------------------------------------------------------------------
 
 @router.get("/{actor_id}")
 def get_threat_actor(
@@ -142,54 +63,8 @@ def get_threat_actor(
 
     **Requires** authentication (any role).
     """
-    actor = db.query(ThreatActor).filter(ThreatActor.id == actor_id).first()
-    if not actor:
-        raise HTTPException(status_code=404, detail="Threat actor not found")
+    return get_actor_detail(db, actor_id)
 
-    # Get associated techniques with their coverage status
-    actor_techniques = (
-        db.query(ThreatActorTechnique, Technique)
-        .join(Technique, ThreatActorTechnique.technique_id == Technique.id)
-        .filter(ThreatActorTechnique.threat_actor_id == actor.id)
-        .order_by(Technique.mitre_id)
-        .all()
-    )
-
-    techniques_list = []
-    for at, tech in actor_techniques:
-        techniques_list.append({
-            "technique_id": str(tech.id),
-            "mitre_id": tech.mitre_id,
-            "name": tech.name,
-            "tactic": tech.tactic,
-            "status_global": tech.status_global.value if tech.status_global else None,
-            "usage_description": at.usage_description,
-            "first_seen_using": at.first_seen_using,
-        })
-
-    return {
-        "id": str(actor.id),
-        "mitre_id": actor.mitre_id,
-        "name": actor.name,
-        "aliases": actor.aliases or [],
-        "description": actor.description,
-        "country": actor.country,
-        "target_sectors": actor.target_sectors or [],
-        "target_regions": actor.target_regions or [],
-        "motivation": actor.motivation,
-        "sophistication": actor.sophistication,
-        "first_seen": actor.first_seen,
-        "last_seen": actor.last_seen,
-        "references": actor.references or [],
-        "mitre_url": actor.mitre_url,
-        "is_active": actor.is_active,
-        "techniques": techniques_list,
-    }
-
-
-# ---------------------------------------------------------------------------
-# GET /threat-actors/{id}/coverage — Cobertura
-# ---------------------------------------------------------------------------
 
 @router.get("/{actor_id}/coverage")
 def get_threat_actor_coverage(
@@ -204,49 +79,8 @@ def get_threat_actor_coverage(
     Returns the percentage of the actor's techniques that have been
     validated or partially validated, along with a breakdown.
     """
-    actor = db.query(ThreatActor).filter(ThreatActor.id == actor_id).first()
-    if not actor:
-        raise HTTPException(status_code=404, detail="Threat actor not found")
+    return get_actor_coverage(db, actor_id)
 
-    # Get all techniques for this actor
-    actor_techniques = (
-        db.query(Technique)
-        .join(ThreatActorTechnique, ThreatActorTechnique.technique_id == Technique.id)
-        .filter(ThreatActorTechnique.threat_actor_id == actor.id)
-        .all()
-    )
-
-    total = len(actor_techniques)
-    if total == 0:
-        return {
-            "actor_id": str(actor.id),
-            "actor_name": actor.name,
-            "total_techniques": 0,
-            "coverage_pct": 0.0,
-            "breakdown": {},
-        }
-
-    breakdown = {}
-    for tech in actor_techniques:
-        status = tech.status_global.value if tech.status_global else "not_evaluated"
-        breakdown[status] = breakdown.get(status, 0) + 1
-
-    covered = breakdown.get("validated", 0) + breakdown.get("partial", 0)
-    coverage_pct = round((covered / total * 100), 1)
-
-    return {
-        "actor_id": str(actor.id),
-        "actor_name": actor.name,
-        "total_techniques": total,
-        "covered": covered,
-        "coverage_pct": coverage_pct,
-        "breakdown": breakdown,
-    }
-
-
-# ---------------------------------------------------------------------------
-# GET /threat-actors/{id}/gaps — Gap analysis
-# ---------------------------------------------------------------------------
 
 @router.get("/{actor_id}/gaps")
 def get_threat_actor_gaps(
@@ -260,52 +94,4 @@ def get_threat_actor_gaps(
 
     Returns list of gap techniques with available templates.
     """
-    actor = db.query(ThreatActor).filter(ThreatActor.id == actor_id).first()
-    if not actor:
-        raise HTTPException(status_code=404, detail="Threat actor not found")
-
-    # Get techniques NOT validated
-    gap_techniques = (
-        db.query(Technique, ThreatActorTechnique)
-        .join(ThreatActorTechnique, ThreatActorTechnique.technique_id == Technique.id)
-        .filter(ThreatActorTechnique.threat_actor_id == actor.id)
-        .filter(Technique.status_global != TechniqueStatus.validated)
-        .order_by(Technique.mitre_id)
-        .all()
-    )
-
-    gaps = []
-    for tech, at in gap_techniques:
-        # Count available templates for this technique
-        template_count = (
-            db.query(TestTemplate)
-            .filter(TestTemplate.mitre_technique_id == tech.mitre_id)
-            .filter(TestTemplate.is_active == True)
-            .count()
-        )
-
-        # Count existing tests
-        test_count = (
-            db.query(Test)
-            .filter(Test.technique_id == tech.id)
-            .count()
-        )
-
-        gaps.append({
-            "technique_id": str(tech.id),
-            "mitre_id": tech.mitre_id,
-            "name": tech.name,
-            "tactic": tech.tactic,
-            "status_global": tech.status_global.value if tech.status_global else None,
-            "usage_description": at.usage_description,
-            "available_templates": template_count,
-            "existing_tests": test_count,
-            "has_templates": template_count > 0,
-        })
-
-    return {
-        "actor_id": str(actor.id),
-        "actor_name": actor.name,
-        "total_gaps": len(gaps),
-        "gaps": gaps,
-    }
+    return get_actor_gaps(db, actor_id)
diff --git a/backend/app/services/threat_actor_service.py b/backend/app/services/threat_actor_service.py
new file mode 100644
index 0000000..03db9ab
--- /dev/null
+++ b/backend/app/services/threat_actor_service.py
@@ -0,0 +1,310 @@
+"""Threat actor data service.
+
+Extracts query and business logic from the threat_actors router so
+that the router remains a thin HTTP adapter.
+
+This module is framework-agnostic: no FastAPI imports.
+"""
+
+from __future__ import annotations
+
+from typing import Any
+
+from sqlalchemy import case, func, or_
+from sqlalchemy.orm import Session
+
+from app.domain.errors import EntityNotFoundError
+from app.models.enums import TechniqueStatus
+from app.models.test import Test
+from app.models.test_template import TestTemplate
+from app.models.threat_actor import ThreatActor, ThreatActorTechnique
+from app.models.technique import Technique
+from app.utils import escape_like
+
+
+# ── Public service functions ──────────────────────────────────────────
+
+
+def list_actors(
+    db: Session,
+    *,
+    search: str | None = None,
+    country: str | None = None,
+    motivation: str | None = None,
+    sophistication: str | None = None,
+    target_sectors: str | None = None,
+    offset: int = 0,
+    limit: int = 50,
+) -> dict[str, Any]:
+    """List threat actors with optional filters, pagination, and coverage stats.
+
+    Uses grouped subqueries to avoid N+1: technique counts and coverage
+    counts are fetched in one query per page.
+    """
+    query = db.query(ThreatActor)
+
+    if search:
+        pattern = f"%{escape_like(search)}%"
+        query = query.filter(
+            or_(
+                ThreatActor.name.ilike(pattern),
+                ThreatActor.description.ilike(pattern),
+                func.cast(ThreatActor.aliases, func.text()).ilike(pattern),
+            )
+        )
+
+    if country:
+        query = query.filter(ThreatActor.country == country)
+
+    if motivation:
+        query = query.filter(ThreatActor.motivation == motivation)
+
+    if sophistication:
+        query = query.filter(ThreatActor.sophistication == sophistication)
+
+    if target_sectors:
+        query = query.filter(
+            func.cast(ThreatActor.target_sectors, func.text()).ilike(
+                f"%{escape_like(target_sectors)}%"
+            )
+        )
+
+    total = query.count()
+    actors = (
+        query.order_by(ThreatActor.name).offset(offset).limit(limit).all()
+    )
+
+    if not actors:
+        return {
+            "total": total,
+            "offset": offset,
+            "limit": limit,
+            "items": [],
+        }
+
+    actor_ids = [a.id for a in actors]
+
+    # Single grouped query: tech_count and covered_count per actor
+    counts_rows = (
+        db.query(
+            ThreatActorTechnique.threat_actor_id,
+            func.count(ThreatActorTechnique.id).label("tech_count"),
+            func.sum(
+                case(
+                    (
+                        Technique.status_global.in_([
+                            TechniqueStatus.validated,
+                            TechniqueStatus.partial,
+                        ]),
+                        1,
+                    ),
+                    else_=0,
+                )
+            ).label("covered_count"),
+        )
+        .join(Technique, ThreatActorTechnique.technique_id == Technique.id)
+        .filter(ThreatActorTechnique.threat_actor_id.in_(actor_ids))
+        .group_by(ThreatActorTechnique.threat_actor_id)
+    ).all()
+
+    counts_map = {
+        str(row.threat_actor_id): {
+            "tech_count": row.tech_count,
+            "covered_count": row.covered_count or 0,
+        }
+        for row in counts_rows
+    }
+
+    results = []
+    for actor in actors:
+        cnt = counts_map.get(str(actor.id), {"tech_count": 0, "covered_count": 0})
+        tech_count = cnt["tech_count"]
+        covered = cnt["covered_count"]
+        coverage_pct = round((covered / tech_count * 100), 1) if tech_count > 0 else 0.0
+
+        results.append({
+            "id": str(actor.id),
+            "mitre_id": actor.mitre_id,
+            "name": actor.name,
+            "aliases": actor.aliases or [],
+            "country": actor.country,
+            "target_sectors": actor.target_sectors or [],
+            "target_regions": actor.target_regions or [],
+            "motivation": actor.motivation,
+            "sophistication": actor.sophistication,
+            "mitre_url": actor.mitre_url,
+            "technique_count": tech_count,
+            "coverage_pct": coverage_pct,
+            "is_active": actor.is_active,
+        })
+
+    return {
+        "total": total,
+        "offset": offset,
+        "limit": limit,
+        "items": results,
+    }
+
+
+def get_actor_detail(db: Session, actor_id: str) -> dict[str, Any]:
+    """Get detailed threat actor with techniques.
+
+    Raises EntityNotFoundError if the actor does not exist.
+    """
+    actor = db.query(ThreatActor).filter(ThreatActor.id == actor_id).first()
+    if not actor:
+        raise EntityNotFoundError("Threat actor", actor_id)
+
+    actor_techniques = (
+        db.query(ThreatActorTechnique, Technique)
+        .join(Technique, ThreatActorTechnique.technique_id == Technique.id)
+        .filter(ThreatActorTechnique.threat_actor_id == actor.id)
+        .order_by(Technique.mitre_id)
+        .all()
+    )
+
+    techniques_list = [
+        {
+            "technique_id": str(tech.id),
+            "mitre_id": tech.mitre_id,
+            "name": tech.name,
+            "tactic": tech.tactic,
+            "status_global": tech.status_global.value if tech.status_global else None,
+            "usage_description": at.usage_description,
+            "first_seen_using": at.first_seen_using,
+        }
+        for at, tech in actor_techniques
+    ]
+
+    return {
+        "id": str(actor.id),
+        "mitre_id": actor.mitre_id,
+        "name": actor.name,
+        "aliases": actor.aliases or [],
+        "description": actor.description,
+        "country": actor.country,
+        "target_sectors": actor.target_sectors or [],
+        "target_regions": actor.target_regions or [],
+        "motivation": actor.motivation,
+        "sophistication": actor.sophistication,
+        "first_seen": actor.first_seen,
+        "last_seen": actor.last_seen,
+        "references": actor.references or [],
+        "mitre_url": actor.mitre_url,
+        "is_active": actor.is_active,
+        "techniques": techniques_list,
+    }
+
+
+def get_actor_coverage(db: Session, actor_id: str) -> dict[str, Any]:
+    """Calculate coverage percentage against a specific threat actor.
+
+    Raises EntityNotFoundError if the actor does not exist.
+    """
+    actor = db.query(ThreatActor).filter(ThreatActor.id == actor_id).first()
+    if not actor:
+        raise EntityNotFoundError("Threat actor", actor_id)
+
+    actor_techniques = (
+        db.query(Technique)
+        .join(ThreatActorTechnique, ThreatActorTechnique.technique_id == Technique.id)
+        .filter(ThreatActorTechnique.threat_actor_id == actor.id)
+        .all()
+    )
+
+    total = len(actor_techniques)
+    if total == 0:
+        return {
+            "actor_id": str(actor.id),
+            "actor_name": actor.name,
+            "total_techniques": 0,
+            "coverage_pct": 0.0,
+            "breakdown": {},
+        }
+
+    breakdown: dict[str, int] = {}
+    for tech in actor_techniques:
+        status = tech.status_global.value if tech.status_global else "not_evaluated"
+        breakdown[status] = breakdown.get(status, 0) + 1
+
+    covered = breakdown.get("validated", 0) + breakdown.get("partial", 0)
+    coverage_pct = round((covered / total * 100), 1)
+
+    return {
+        "actor_id": str(actor.id),
+        "actor_name": actor.name,
+        "total_techniques": total,
+        "covered": covered,
+        "coverage_pct": coverage_pct,
+        "breakdown": breakdown,
+    }
+
+
+def get_actor_gaps(db: Session, actor_id: str) -> dict[str, Any]:
+    """Identify techniques of this actor that are not fully validated.
+
+    Raises EntityNotFoundError if the actor does not exist.
+    """
+    actor = db.query(ThreatActor).filter(ThreatActor.id == actor_id).first()
+    if not actor:
+        raise EntityNotFoundError("Threat actor", actor_id)
+
+    gap_techniques = (
+        db.query(Technique, ThreatActorTechnique)
+        .join(ThreatActorTechnique, ThreatActorTechnique.technique_id == Technique.id)
+        .filter(ThreatActorTechnique.threat_actor_id == actor.id)
+        .filter(Technique.status_global != TechniqueStatus.validated)
+        .order_by(Technique.mitre_id)
+        .all()
+    )
+
+    if not gap_techniques:
+        return {
+            "actor_id": str(actor.id),
+            "actor_name": actor.name,
+            "total_gaps": 0,
+            "gaps": [],
+        }
+
+    technique_ids = [tech.id for tech, _ in gap_techniques]
+    mitre_ids = [tech.mitre_id for tech, _ in gap_techniques]
+
+    # Batch template counts by mitre_technique_id
+    template_counts = (
+        db.query(TestTemplate.mitre_technique_id, func.count(TestTemplate.id).label("cnt"))
+        .filter(TestTemplate.mitre_technique_id.in_(mitre_ids))
+        .filter(TestTemplate.is_active == True)
+        .group_by(TestTemplate.mitre_technique_id)
+    ).all()
+    template_map = {row.mitre_technique_id: row.cnt for row in template_counts}
+
+    # Batch test counts by technique_id
+    test_counts = (
+        db.query(Test.technique_id, func.count(Test.id).label("cnt"))
+        .filter(Test.technique_id.in_(technique_ids))
+        .group_by(Test.technique_id)
+    ).all()
+    test_map = {str(row.technique_id): row.cnt for row in test_counts}
+
+    gaps = []
+    for tech, at in gap_techniques:
+        template_count = template_map.get(tech.mitre_id, 0)
+        test_count = test_map.get(str(tech.id), 0)
+        gaps.append({
+            "technique_id": str(tech.id),
+            "mitre_id": tech.mitre_id,
+            "name": tech.name,
+            "tactic": tech.tactic,
+            "status_global": tech.status_global.value if tech.status_global else None,
+            "usage_description": at.usage_description,
+            "available_templates": template_count,
+            "existing_tests": test_count,
+            "has_templates": template_count > 0,
+        })
+
+    return {
+        "actor_id": str(actor.id),
+        "actor_name": actor.name,
+        "total_gaps": len(gaps),
+        "gaps": gaps,
+    }