diff --git a/backend/alembic/versions/b026_add_technique_query_indexes.py b/backend/alembic/versions/b026_add_technique_query_indexes.py
new file mode 100644
index 0000000..e62dc89
--- /dev/null
+++ b/backend/alembic/versions/b026_add_technique_query_indexes.py
@@ -0,0 +1,38 @@
+"""add_technique_query_indexes
+
+Add indexes on techniques table for common query patterns
+(filter by tactic, filter by status_global) used in heatmap, scoring,
+and list-all-techniques operations.
+
+These may already exist if the ORM model auto-created them; the
+``if_not_exists`` flag makes this migration safe to run regardless.
+
+Revision ID: b026techidx
+Revises: b025uqtdr
+Create Date: 2026-02-18 18:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+
+revision: str = "b026techidx"
+down_revision: Union[str, None] = "b025uqtdr"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.execute(
+        "CREATE INDEX IF NOT EXISTS ix_techniques_tactic "
+        "ON techniques (tactic)"
+    )
+    op.execute(
+        "CREATE INDEX IF NOT EXISTS ix_techniques_status_global "
+        "ON techniques (status_global)"
+    )
+
+
+def downgrade() -> None:
+    op.drop_index("ix_techniques_status_global", table_name="techniques")
+    op.drop_index("ix_techniques_tactic", table_name="techniques")
diff --git a/backend/app/dependencies/repositories.py b/backend/app/dependencies/repositories.py
new file mode 100644
index 0000000..eae5d62
--- /dev/null
+++ b/backend/app/dependencies/repositories.py
@@ -0,0 +1,30 @@
+"""FastAPI dependency providers for repositories.
+
+Wiring lives ONLY in the presentation layer — use cases and services
+never know which concrete repository implementation they receive.
+"""
+
+from fastapi import Depends
+from sqlalchemy.orm import Session
+
+from app.database import get_db
+from app.infrastructure.persistence.repositories.sa_technique_repository import (
+    SATechniqueRepository,
+)
+from app.infrastructure.persistence.repositories.sa_test_repository import (
+    SATestRepository,
+)
+
+
+def get_technique_repository(
+    db: Session = Depends(get_db),
+) -> SATechniqueRepository:
+    """Provide a TechniqueRepository backed by the current DB session."""
+    return SATechniqueRepository(db)
+
+
+def get_test_repository(
+    db: Session = Depends(get_db),
+) -> SATestRepository:
+    """Provide a TestRepository backed by the current DB session."""
+    return SATestRepository(db)
diff --git a/backend/app/infrastructure/persistence/__init__.py b/backend/app/infrastructure/persistence/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/backend/app/infrastructure/persistence/mappers/__init__.py b/backend/app/infrastructure/persistence/mappers/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/backend/app/infrastructure/persistence/mappers/technique_mapper.py b/backend/app/infrastructure/persistence/mappers/technique_mapper.py
new file mode 100644
index 0000000..74cd588
--- /dev/null
+++ b/backend/app/infrastructure/persistence/mappers/technique_mapper.py
@@ -0,0 +1,20 @@
+"""Technique ORM model <-> domain entity mapper."""
+
+from __future__ import annotations
+
+from app.domain.entities.technique import TechniqueEntity
+from app.domain.enums import TechniqueStatus
+
+
+class TechniqueMapper:
+    """Converts between SQLAlchemy Technique model and TechniqueEntity."""
+
+    @staticmethod
+    def to_entity(model: object) -> TechniqueEntity:
+        """Convert an ORM Technique model to a domain TechniqueEntity."""
+        return TechniqueEntity.from_orm(model)
+
+    @staticmethod
+    def to_model_updates(entity: TechniqueEntity, model: object) -> None:
+        """Apply entity changes back onto an existing ORM model."""
+        entity.apply_to(model)
diff --git a/backend/app/infrastructure/persistence/repositories/__init__.py b/backend/app/infrastructure/persistence/repositories/__init__.py
new file mode 100644
index 0000000..d6c0338
--- /dev/null
+++ b/backend/app/infrastructure/persistence/repositories/__init__.py
@@ -0,0 +1,8 @@
+from app.infrastructure.persistence.repositories.sa_technique_repository import (
+    SATechniqueRepository,
+)
+from app.infrastructure.persistence.repositories.sa_test_repository import (
+    SATestRepository,
+)
+
+__all__ = ["SATechniqueRepository", "SATestRepository"]
diff --git a/backend/app/infrastructure/persistence/repositories/sa_technique_repository.py b/backend/app/infrastructure/persistence/repositories/sa_technique_repository.py
new file mode 100644
index 0000000..84fb08e
--- /dev/null
+++ b/backend/app/infrastructure/persistence/repositories/sa_technique_repository.py
@@ -0,0 +1,199 @@
+"""SQLAlchemy implementation of TechniqueRepository.
+
+Receives a Session from the caller — does NOT create its own.
+Does NOT call commit() — the Unit of Work owns that.
+"""
+
+from __future__ import annotations
+
+import uuid
+
+from sqlalchemy import func
+from sqlalchemy.orm import Session
+
+from app.domain.entities.technique import TechniqueEntity
+from app.domain.enums import TechniqueStatus, TestState
+from app.domain.ports.repositories.technique_repository import TechniqueWithCounts
+from app.infrastructure.persistence.mappers.technique_mapper import TechniqueMapper
+from app.models.detection_rule import DetectionRule
+from app.models.technique import Technique
+from app.models.test import Test
+
+
+class SATechniqueRepository:
+    """Concrete repository backed by SQLAlchemy."""
+
+    def __init__(self, session: Session) -> None:
+        self._session = session
+
+    # -- Single-entity access ----------------------------------------------
+
+    def find_by_id(self, technique_id: uuid.UUID) -> TechniqueEntity | None:
+        model = (
+            self._session.query(Technique)
+            .filter(Technique.id == technique_id)
+            .first()
+        )
+        return TechniqueMapper.to_entity(model) if model else None
+
+    def find_by_mitre_id(self, mitre_id: str) -> TechniqueEntity | None:
+        model = (
+            self._session.query(Technique)
+            .filter(Technique.mitre_id == mitre_id)
+            .first()
+        )
+        return TechniqueMapper.to_entity(model) if model else None
+
+    # -- List access -------------------------------------------------------
+
+    def list_all(
+        self,
+        *,
+        tactic: str | None = None,
+        status: TechniqueStatus | None = None,
+        review_required: bool | None = None,
+    ) -> list[TechniqueEntity]:
+        query = self._session.query(Technique)
+        if tactic is not None:
+            query = query.filter(Technique.tactic == tactic)
+        if status is not None:
+            query = query.filter(Technique.status_global == status)
+        if review_required is not None:
+            query = query.filter(Technique.review_required == review_required)
+        models = query.order_by(Technique.mitre_id).all()
+        return [TechniqueMapper.to_entity(m) for m in models]
+
+    def list_by_ids(self, ids: list[uuid.UUID]) -> list[TechniqueEntity]:
+        if not ids:
+            return []
+        models = (
+            self._session.query(Technique)
+            .filter(Technique.id.in_(ids))
+            .all()
+        )
+        return [TechniqueMapper.to_entity(m) for m in models]
+
+    # -- Batch queries (for scoring/heatmap) -------------------------------
+
+    def count_by_status(self) -> dict[TechniqueStatus, int]:
+        rows = (
+            self._session.query(
+                Technique.status_global,
+                func.count(Technique.id),
+            )
+            .group_by(Technique.status_global)
+            .all()
+        )
+        result = {s: 0 for s in TechniqueStatus}
+        for status_val, count in rows:
+            key = (
+                status_val
+                if isinstance(status_val, TechniqueStatus)
+                else TechniqueStatus(status_val)
+            )
+            result[key] = count
+        return result
+
+    def find_all_with_test_counts(self) -> list[TechniqueWithCounts]:
+        """Single query replacing the N+1 pattern.
+
+        Returns all techniques with pre-aggregated test and detection
+        rule counts via subqueries.
+        """
+        test_count_sq = (
+            self._session.query(
+                Test.technique_id,
+                func.count(Test.id).label("test_count"),
+                func.sum(
+                    func.cast(Test.state == TestState.validated, self._int_type())
+                ).label("validated_count"),
+            )
+            .group_by(Test.technique_id)
+            .subquery()
+        )
+        rule_count_sq = (
+            self._session.query(
+                DetectionRule.mitre_technique_id,
+                func.count(DetectionRule.id).label("rule_count"),
+            )
+            .group_by(DetectionRule.mitre_technique_id)
+            .subquery()
+        )
+
+        rows = (
+            self._session.query(
+                Technique,
+                func.coalesce(test_count_sq.c.test_count, 0),
+                func.coalesce(test_count_sq.c.validated_count, 0),
+                func.coalesce(rule_count_sq.c.rule_count, 0),
+            )
+            .outerjoin(test_count_sq, Technique.id == test_count_sq.c.technique_id)
+            .outerjoin(
+                rule_count_sq,
+                Technique.mitre_id == rule_count_sq.c.mitre_technique_id,
+            )
+            .order_by(Technique.mitre_id)
+            .all()
+        )
+
+        return [
+            TechniqueWithCounts(
+                entity=TechniqueMapper.to_entity(tech),
+                test_count=int(tc),
+                validated_test_count=int(vtc),
+                detection_rule_count=int(rc),
+            )
+            for tech, tc, vtc, rc in rows
+        ]
+
+    # -- Mutations ---------------------------------------------------------
+
+    def save(self, technique: TechniqueEntity) -> TechniqueEntity:
+        existing = (
+            self._session.query(Technique)
+            .filter(Technique.id == technique.id)
+            .first()
+        )
+        if existing:
+            technique.apply_to(existing)
+            existing.mitre_id = technique.mitre_id
+            existing.name = technique.name
+            existing.tactic = technique.tactic
+            existing.description = technique.description
+            existing.platforms = technique.platforms
+            existing.is_subtechnique = technique.is_subtechnique
+            existing.parent_mitre_id = technique.parent_mitre_id
+            self._session.flush()
+            return TechniqueMapper.to_entity(existing)
+        else:
+            model = Technique(
+                id=technique.id,
+                mitre_id=technique.mitre_id,
+                name=technique.name,
+                tactic=technique.tactic,
+                description=technique.description,
+                platforms=technique.platforms,
+                is_subtechnique=technique.is_subtechnique,
+                parent_mitre_id=technique.parent_mitre_id,
+                status_global=technique.status_global,
+                review_required=technique.review_required,
+                last_review_date=technique.last_review_date,
+            )
+            self._session.add(model)
+            self._session.flush()
+            return TechniqueMapper.to_entity(model)
+
+    def exists_by_mitre_id(self, mitre_id: str) -> bool:
+        return (
+            self._session.query(Technique.id)
+            .filter(Technique.mitre_id == mitre_id)
+            .first()
+        ) is not None
+
+    # -- Internal ----------------------------------------------------------
+
+    @staticmethod
+    def _int_type():
+        """Return an Integer type for CAST expressions (SQLite-compatible)."""
+        from sqlalchemy import Integer
+        return Integer
diff --git a/backend/app/infrastructure/persistence/repositories/sa_test_repository.py b/backend/app/infrastructure/persistence/repositories/sa_test_repository.py
new file mode 100644
index 0000000..0a893f8
--- /dev/null
+++ b/backend/app/infrastructure/persistence/repositories/sa_test_repository.py
@@ -0,0 +1,86 @@
+"""SQLAlchemy implementation of TestRepository."""
+
+from __future__ import annotations
+
+import uuid
+
+from sqlalchemy import func
+from sqlalchemy.orm import Session
+
+from app.domain.enums import TestState
+from app.models.test import Test
+
+
+class SATestRepository:
+    """Concrete test repository backed by SQLAlchemy."""
+
+    def __init__(self, session: Session) -> None:
+        self._session = session
+
+    def find_by_id(self, test_id: uuid.UUID) -> Test | None:
+        return (
+            self._session.query(Test)
+            .filter(Test.id == test_id)
+            .first()
+        )
+
+    def list_by_technique(self, technique_id: uuid.UUID) -> list[Test]:
+        return (
+            self._session.query(Test)
+            .filter(Test.technique_id == technique_id)
+            .order_by(Test.created_at)
+            .all()
+        )
+
+    def list_by_state(self, state: TestState) -> list[Test]:
+        return (
+            self._session.query(Test)
+            .filter(Test.state == state)
+            .all()
+        )
+
+    def count_by_technique_and_state(
+        self,
+        technique_id: uuid.UUID,
+    ) -> dict[TestState, int]:
+        rows = (
+            self._session.query(Test.state, func.count(Test.id))
+            .filter(Test.technique_id == technique_id)
+            .group_by(Test.state)
+            .all()
+        )
+        result: dict[TestState, int] = {}
+        for state_val, count in rows:
+            key = (
+                state_val
+                if isinstance(state_val, TestState)
+                else TestState(state_val)
+            )
+            result[key] = count
+        return result
+
+    def get_states_and_results_for_technique(
+        self,
+        technique_id: uuid.UUID,
+    ) -> list[tuple[str, str | None]]:
+        """Return lightweight (state, detection_result) pairs.
+
+        Used by TechniqueEntity.recalculate_status() without loading
+        full Test models.
+        """
+        rows = (
+            self._session.query(Test.state, Test.detection_result)
+            .filter(Test.technique_id == technique_id)
+            .all()
+        )
+        return [
+            (
+                r.state.value if hasattr(r.state, "value") else str(r.state),
+                (
+                    r.detection_result.value
+                    if hasattr(r.detection_result, "value")
+                    else r.detection_result
+                ),
+            )
+            for r in rows
+        ]
diff --git a/backend/tests/test_repositories.py b/backend/tests/test_repositories.py
new file mode 100644
index 0000000..f42cacf
--- /dev/null
+++ b/backend/tests/test_repositories.py
@@ -0,0 +1,237 @@
+"""Integration tests for repository implementations.
+
+Uses the SQLite-based ``db`` fixture from conftest.py.
+"""
+
+import uuid
+
+import pytest
+
+from app.domain.entities.technique import TechniqueEntity
+from app.domain.enums import TechniqueStatus, TestState
+from app.infrastructure.persistence.repositories.sa_technique_repository import (
+    SATechniqueRepository,
+)
+from app.infrastructure.persistence.repositories.sa_test_repository import (
+    SATestRepository,
+)
+from app.models.technique import Technique
+from app.models.test import Test
+
+
+# ── Helpers ──────────────────────────────────────────────────────────
+
+
+def _create_technique(db, mitre_id="T1059", name="Test Technique", **kwargs):
+    tech = Technique(
+        id=uuid.uuid4(),
+        mitre_id=mitre_id,
+        name=name,
+        tactic=kwargs.get("tactic", "execution"),
+        status_global=kwargs.get("status_global", TechniqueStatus.not_evaluated),
+    )
+    db.add(tech)
+    db.flush()
+    return tech
+
+
+def _create_test(db, technique, state=TestState.draft, **kwargs):
+    t = Test(
+        id=uuid.uuid4(),
+        technique_id=technique.id,
+        name=kwargs.get("name", "Test 1"),
+        state=state,
+        detection_result=kwargs.get("detection_result"),
+    )
+    db.add(t)
+    db.flush()
+    return t
+
+
+# ── SATechniqueRepository ───────────────────────────────────────────
+
+
+class TestSATechniqueRepository:
+
+    def test_find_by_id_returns_entity(self, db):
+        tech = _create_technique(db)
+        db.commit()
+        repo = SATechniqueRepository(db)
+
+        result = repo.find_by_id(tech.id)
+        assert result is not None
+        assert result.mitre_id == "T1059"
+        assert isinstance(result, TechniqueEntity)
+
+    def test_find_by_id_not_found(self, db):
+        repo = SATechniqueRepository(db)
+        assert repo.find_by_id(uuid.uuid4()) is None
+
+    def test_find_by_mitre_id(self, db):
+        _create_technique(db, mitre_id="T1548")
+        db.commit()
+        repo = SATechniqueRepository(db)
+
+        result = repo.find_by_mitre_id("T1548")
+        assert result is not None
+        assert result.mitre_id == "T1548"
+
+    def test_find_by_mitre_id_not_found(self, db):
+        repo = SATechniqueRepository(db)
+        assert repo.find_by_mitre_id("T9999") is None
+
+    def test_list_all_no_filters(self, db):
+        _create_technique(db, mitre_id="T1059", name="A")
+        _create_technique(db, mitre_id="T1060", name="B")
+        db.commit()
+        repo = SATechniqueRepository(db)
+
+        results = repo.list_all()
+        assert len(results) == 2
+        assert results[0].mitre_id == "T1059"
+        assert results[1].mitre_id == "T1060"
+
+    def test_list_all_filter_by_tactic(self, db):
+        _create_technique(db, mitre_id="T1059", tactic="execution")
+        _create_technique(db, mitre_id="T1060", tactic="persistence")
+        db.commit()
+        repo = SATechniqueRepository(db)
+
+        results = repo.list_all(tactic="execution")
+        assert len(results) == 1
+        assert results[0].mitre_id == "T1059"
+
+    def test_list_all_filter_by_status(self, db):
+        _create_technique(db, mitre_id="T1059", status_global=TechniqueStatus.validated)
+        _create_technique(db, mitre_id="T1060", status_global=TechniqueStatus.not_evaluated)
+        db.commit()
+        repo = SATechniqueRepository(db)
+
+        results = repo.list_all(status=TechniqueStatus.validated)
+        assert len(results) == 1
+        assert results[0].mitre_id == "T1059"
+
+    def test_list_by_ids(self, db):
+        t1 = _create_technique(db, mitre_id="T1059")
+        _create_technique(db, mitre_id="T1060")
+        db.commit()
+        repo = SATechniqueRepository(db)
+
+        results = repo.list_by_ids([t1.id])
+        assert len(results) == 1
+        assert results[0].mitre_id == "T1059"
+
+    def test_list_by_ids_empty(self, db):
+        repo = SATechniqueRepository(db)
+        assert repo.list_by_ids([]) == []
+
+    def test_count_by_status(self, db):
+        _create_technique(db, mitre_id="T1059", status_global=TechniqueStatus.validated)
+        _create_technique(db, mitre_id="T1060", status_global=TechniqueStatus.validated)
+        _create_technique(db, mitre_id="T1061", status_global=TechniqueStatus.not_evaluated)
+        db.commit()
+        repo = SATechniqueRepository(db)
+
+        counts = repo.count_by_status()
+        assert counts[TechniqueStatus.validated] == 2
+        assert counts[TechniqueStatus.not_evaluated] == 1
+        assert counts[TechniqueStatus.partial] == 0
+
+    def test_exists_by_mitre_id(self, db):
+        _create_technique(db, mitre_id="T1059")
+        db.commit()
+        repo = SATechniqueRepository(db)
+
+        assert repo.exists_by_mitre_id("T1059") is True
+        assert repo.exists_by_mitre_id("T9999") is False
+
+    def test_save_new_technique(self, db):
+        repo = SATechniqueRepository(db)
+        entity = TechniqueEntity.create(
+            mitre_id="T2000",
+            name="New Technique",
+            tactic="discovery",
+        )
+        saved = repo.save(entity)
+        db.commit()
+
+        assert saved.mitre_id == "T2000"
+        assert repo.find_by_mitre_id("T2000") is not None
+
+    def test_save_updates_existing(self, db):
+        tech = _create_technique(db, mitre_id="T1059")
+        db.commit()
+        repo = SATechniqueRepository(db)
+
+        entity = repo.find_by_id(tech.id)
+        entity.status_global = TechniqueStatus.validated
+        saved = repo.save(entity)
+        db.commit()
+
+        reloaded = repo.find_by_id(tech.id)
+        assert reloaded.status_global == TechniqueStatus.validated
+
+
+# ── SATestRepository ─────────────────────────────────────────────────
+
+
+class TestSATestRepository:
+
+    def test_find_by_id(self, db):
+        tech = _create_technique(db)
+        test = _create_test(db, tech)
+        db.commit()
+        repo = SATestRepository(db)
+
+        result = repo.find_by_id(test.id)
+        assert result is not None
+        assert result.id == test.id
+
+    def test_find_by_id_not_found(self, db):
+        repo = SATestRepository(db)
+        assert repo.find_by_id(uuid.uuid4()) is None
+
+    def test_list_by_technique(self, db):
+        tech = _create_technique(db)
+        _create_test(db, tech, name="Test A")
+        _create_test(db, tech, name="Test B")
+        db.commit()
+        repo = SATestRepository(db)
+
+        results = repo.list_by_technique(tech.id)
+        assert len(results) == 2
+
+    def test_list_by_state(self, db):
+        tech = _create_technique(db)
+        _create_test(db, tech, state=TestState.draft)
+        _create_test(db, tech, state=TestState.validated)
+        db.commit()
+        repo = SATestRepository(db)
+
+        drafts = repo.list_by_state(TestState.draft)
+        assert len(drafts) == 1
+
+    def test_count_by_technique_and_state(self, db):
+        tech = _create_technique(db)
+        _create_test(db, tech, state=TestState.draft)
+        _create_test(db, tech, state=TestState.draft)
+        _create_test(db, tech, state=TestState.validated)
+        db.commit()
+        repo = SATestRepository(db)
+
+        counts = repo.count_by_technique_and_state(tech.id)
+        assert counts.get(TestState.draft) == 2
+        assert counts.get(TestState.validated) == 1
+
+    def test_get_states_and_results(self, db):
+        tech = _create_technique(db)
+        _create_test(db, tech, state=TestState.validated, detection_result="detected")
+        _create_test(db, tech, state=TestState.draft)
+        db.commit()
+        repo = SATestRepository(db)
+
+        pairs = repo.get_states_and_results_for_technique(tech.id)
+        assert len(pairs) == 2
+        states = [p[0] for p in pairs]
+        assert "validated" in states
+        assert "draft" in states