diff --git a/.gitignore b/.gitignore
index 8e18115..f5ea313 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,5 +14,6 @@ coverage/
 bin/
 obj/
 data/
+!backend/src/features/*/data/*.ts
 MotoVaultPro.csproj.user
 Properties/launchSettings.json
diff --git a/backend/src/features/fuel-logs/data/fuel-logs.repository.ts b/backend/src/features/fuel-logs/data/fuel-logs.repository.ts
new file mode 100644
index 0000000..54a04df
--- /dev/null
+++ b/backend/src/features/fuel-logs/data/fuel-logs.repository.ts
@@ -0,0 +1,209 @@
+/**
+ * @ai-summary Data access layer for fuel logs
+ * @ai-context Handles database operations and MPG calculations
+ */
+
+import { Pool } from 'pg';
+import { FuelLog, CreateFuelLogRequest, FuelStats } from '../domain/fuel-logs.types';
+
+export class FuelLogsRepository {
+  constructor(private pool: Pool) {}
+
+  async create(data: CreateFuelLogRequest & { userId: string, mpg?: number }): Promise<FuelLog> {
+    const query = `
+      INSERT INTO fuel_logs (
+        user_id, vehicle_id, date, odometer, gallons,
+        price_per_gallon, total_cost, station, location, notes, mpg
+      )
+      VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)
+      RETURNING *
+    `;
+    
+    const values = [
+      data.userId,
+      data.vehicleId,
+      data.date,
+      data.odometer,
+      data.gallons,
+      data.pricePerGallon,
+      data.totalCost,
+      data.station,
+      data.location,
+      data.notes,
+      data.mpg
+    ];
+
+    const result = await this.pool.query(query, values);
+    return this.mapRow(result.rows[0]);
+  }
+
+  async findByVehicleId(vehicleId: string): Promise<FuelLog[]> {
+    const query = `
+      SELECT * FROM fuel_logs
+      WHERE vehicle_id = $1
+      ORDER BY date DESC, created_at DESC
+    `;
+    
+    const result = await this.pool.query(query, [vehicleId]);
+    return result.rows.map(row => this.mapRow(row));
+  }
+
+  async findByUserId(userId: string): Promise<FuelLog[]> {
+    const query = `
+      SELECT * FROM fuel_logs
+      WHERE user_id = $1
+      ORDER BY date DESC, created_at DESC
+    `;
+    
+    const result = await this.pool.query(query, [userId]);
+    return result.rows.map(row => this.mapRow(row));
+  }
+
+  async findById(id: string): Promise<FuelLog | null> {
+    const query = 'SELECT * FROM fuel_logs WHERE id = $1';
+    const result = await this.pool.query(query, [id]);
+    
+    if (result.rows.length === 0) {
+      return null;
+    }
+    
+    return this.mapRow(result.rows[0]);
+  }
+
+  async getPreviousLog(vehicleId: string, date: string, odometer: number): Promise<FuelLog | null> {
+    const query = `
+      SELECT * FROM fuel_logs
+      WHERE vehicle_id = $1
+        AND (date < $2 OR (date = $2 AND odometer < $3))
+      ORDER BY date DESC, odometer DESC
+      LIMIT 1
+    `;
+    
+    const result = await this.pool.query(query, [vehicleId, date, odometer]);
+    
+    if (result.rows.length === 0) {
+      return null;
+    }
+    
+    return this.mapRow(result.rows[0]);
+  }
+
+  async update(id: string, data: Partial<FuelLog>): Promise<FuelLog | null> {
+    const fields = [];
+    const values = [];
+    let paramCount = 1;
+
+    // Build dynamic update query
+    if (data.date !== undefined) {
+      fields.push(`date = $${paramCount++}`);
+      values.push(data.date);
+    }
+    if (data.odometer !== undefined) {
+      fields.push(`odometer = $${paramCount++}`);
+      values.push(data.odometer);
+    }
+    if (data.gallons !== undefined) {
+      fields.push(`gallons = $${paramCount++}`);
+      values.push(data.gallons);
+    }
+    if (data.pricePerGallon !== undefined) {
+      fields.push(`price_per_gallon = $${paramCount++}`);
+      values.push(data.pricePerGallon);
+    }
+    if (data.totalCost !== undefined) {
+      fields.push(`total_cost = $${paramCount++}`);
+      values.push(data.totalCost);
+    }
+    if (data.station !== undefined) {
+      fields.push(`station = $${paramCount++}`);
+      values.push(data.station);
+    }
+    if (data.location !== undefined) {
+      fields.push(`location = $${paramCount++}`);
+      values.push(data.location);
+    }
+    if (data.notes !== undefined) {
+      fields.push(`notes = $${paramCount++}`);
+      values.push(data.notes);
+    }
+    if (data.mpg !== undefined) {
+      fields.push(`mpg = $${paramCount++}`);
+      values.push(data.mpg);
+    }
+
+    if (fields.length === 0) {
+      return this.findById(id);
+    }
+
+    values.push(id);
+    const query = `
+      UPDATE fuel_logs
+      SET ${fields.join(', ')}
+      WHERE id = $${paramCount}
+      RETURNING *
+    `;
+
+    const result = await this.pool.query(query, values);
+    
+    if (result.rows.length === 0) {
+      return null;
+    }
+    
+    return this.mapRow(result.rows[0]);
+  }
+
+  async delete(id: string): Promise<boolean> {
+    const query = 'DELETE FROM fuel_logs WHERE id = $1';
+    const result = await this.pool.query(query, [id]);
+    return (result.rowCount ?? 0) > 0;
+  }
+
+  async getStats(vehicleId: string): Promise<FuelStats | null> {
+    const query = `
+      SELECT 
+        COUNT(*) as log_count,
+        SUM(gallons) as total_gallons,
+        SUM(total_cost) as total_cost,
+        AVG(price_per_gallon) as avg_price_per_gallon,
+        AVG(mpg) as avg_mpg,
+        MAX(odometer) - MIN(odometer) as total_miles
+      FROM fuel_logs
+      WHERE vehicle_id = $1
+    `;
+    
+    const result = await this.pool.query(query, [vehicleId]);
+    
+    if (result.rows.length === 0 || result.rows[0].log_count === '0') {
+      return null;
+    }
+    
+    const row = result.rows[0];
+    return {
+      logCount: parseInt(row.log_count),
+      totalGallons: parseFloat(row.total_gallons) || 0,
+      totalCost: parseFloat(row.total_cost) || 0,
+      averagePricePerGallon: parseFloat(row.avg_price_per_gallon) || 0,
+      averageMPG: parseFloat(row.avg_mpg) || 0,
+      totalMiles: parseInt(row.total_miles) || 0,
+    };
+  }
+
+  private mapRow(row: any): FuelLog {
+    return {
+      id: row.id,
+      userId: row.user_id,
+      vehicleId: row.vehicle_id,
+      date: row.date,
+      odometer: row.odometer,
+      gallons: parseFloat(row.gallons),
+      pricePerGallon: parseFloat(row.price_per_gallon),
+      totalCost: parseFloat(row.total_cost),
+      station: row.station,
+      location: row.location,
+      notes: row.notes,
+      mpg: row.mpg ? parseFloat(row.mpg) : undefined,
+      createdAt: row.created_at,
+      updatedAt: row.updated_at,
+    };
+  }
+}
\ No newline at end of file
diff --git a/backend/src/features/stations/data/stations.repository.ts b/backend/src/features/stations/data/stations.repository.ts
new file mode 100644
index 0000000..7c3db03
--- /dev/null
+++ b/backend/src/features/stations/data/stations.repository.ts
@@ -0,0 +1,117 @@
+/**
+ * @ai-summary Data access layer for stations
+ */
+
+import { Pool } from 'pg';
+import { Station, SavedStation } from '../domain/stations.types';
+
+export class StationsRepository {
+  constructor(private pool: Pool) {}
+
+  async cacheStation(station: Station): Promise<void> {
+    const query = `
+      INSERT INTO station_cache (
+        place_id, name, address, latitude, longitude,
+        price_regular, price_premium, price_diesel, rating, photo_url
+      )
+      VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)
+      ON CONFLICT (place_id) DO UPDATE
+      SET name = $2, address = $3, latitude = $4, longitude = $5,
+          rating = $9, photo_url = $10, cached_at = NOW()
+    `;
+    
+    await this.pool.query(query, [
+      station.placeId,
+      station.name,
+      station.address,
+      station.latitude,
+      station.longitude,
+      station.priceRegular,
+      station.pricePremium,
+      station.priceDiesel,
+      station.rating,
+      station.photoUrl
+    ]);
+  }
+
+  async getCachedStation(placeId: string): Promise<Station | null> {
+    const query = 'SELECT * FROM station_cache WHERE place_id = $1';
+    const result = await this.pool.query(query, [placeId]);
+    
+    if (result.rows.length === 0) {
+      return null;
+    }
+    
+    return this.mapCacheRow(result.rows[0]);
+  }
+
+  async saveStation(userId: string, placeId: string, data?: { nickname?: string; notes?: string; isFavorite?: boolean }): Promise<SavedStation> {
+    const query = `
+      INSERT INTO saved_stations (user_id, place_id, nickname, notes, is_favorite)
+      VALUES ($1, $2, $3, $4, $5)
+      ON CONFLICT (user_id, place_id) DO UPDATE
+      SET nickname = COALESCE($3, saved_stations.nickname),
+          notes = COALESCE($4, saved_stations.notes),
+          is_favorite = COALESCE($5, saved_stations.is_favorite),
+          updated_at = NOW()
+      RETURNING *
+    `;
+    
+    const result = await this.pool.query(query, [
+      userId,
+      placeId,
+      data?.nickname,
+      data?.notes,
+      data?.isFavorite || false
+    ]);
+    
+    return this.mapSavedRow(result.rows[0]);
+  }
+
+  async getUserSavedStations(userId: string): Promise<SavedStation[]> {
+    const query = `
+      SELECT * FROM saved_stations
+      WHERE user_id = $1
+      ORDER BY is_favorite DESC, created_at DESC
+    `;
+    
+    const result = await this.pool.query(query, [userId]);
+    return result.rows.map(row => this.mapSavedRow(row));
+  }
+
+  async deleteSavedStation(userId: string, placeId: string): Promise<boolean> {
+    const query = 'DELETE FROM saved_stations WHERE user_id = $1 AND place_id = $2';
+    const result = await this.pool.query(query, [userId, placeId]);
+    return (result.rowCount ?? 0) > 0;
+  }
+
+  private mapCacheRow(row: any): Station {
+    return {
+      id: row.id,
+      placeId: row.place_id,
+      name: row.name,
+      address: row.address,
+      latitude: parseFloat(row.latitude),
+      longitude: parseFloat(row.longitude),
+      priceRegular: row.price_regular ? parseFloat(row.price_regular) : undefined,
+      pricePremium: row.price_premium ? parseFloat(row.price_premium) : undefined,
+      priceDiesel: row.price_diesel ? parseFloat(row.price_diesel) : undefined,
+      rating: row.rating ? parseFloat(row.rating) : undefined,
+      photoUrl: row.photo_url,
+      lastUpdated: row.cached_at
+    };
+  }
+
+  private mapSavedRow(row: any): SavedStation {
+    return {
+      id: row.id,
+      userId: row.user_id,
+      stationId: row.place_id,
+      nickname: row.nickname,
+      notes: row.notes,
+      isFavorite: row.is_favorite,
+      createdAt: row.created_at,
+      updatedAt: row.updated_at
+    };
+  }
+}
\ No newline at end of file
diff --git a/backend/src/features/vehicles/data/vehicles.repository.ts b/backend/src/features/vehicles/data/vehicles.repository.ts
new file mode 100644
index 0000000..f241a61
--- /dev/null
+++ b/backend/src/features/vehicles/data/vehicles.repository.ts
@@ -0,0 +1,177 @@
+/**
+ * @ai-summary Data access layer for vehicles
+ * @ai-context All database operations, no business logic
+ */
+
+import { Pool } from 'pg';
+import { Vehicle, CreateVehicleRequest } from '../domain/vehicles.types';
+
+export class VehiclesRepository {
+  constructor(private pool: Pool) {}
+
+  async create(data: CreateVehicleRequest & { userId: string, make?: string, model?: string, year?: number }): Promise<Vehicle> {
+    const query = `
+      INSERT INTO vehicles (
+        user_id, vin, make, model, year, 
+        nickname, color, license_plate, odometer_reading
+      )
+      VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)
+      RETURNING *
+    `;
+    
+    const values = [
+      data.userId,
+      data.vin,
+      data.make,
+      data.model,
+      data.year,
+      data.nickname,
+      data.color,
+      data.licensePlate,
+      data.odometerReading || 0
+    ];
+
+    const result = await this.pool.query(query, values);
+    return this.mapRow(result.rows[0]);
+  }
+
+  async findByUserId(userId: string): Promise<Vehicle[]> {
+    const query = `
+      SELECT * FROM vehicles
+      WHERE user_id = $1 AND is_active = true
+      ORDER BY created_at DESC
+    `;
+    
+    const result = await this.pool.query(query, [userId]);
+    return result.rows.map(row => this.mapRow(row));
+  }
+
+  async findById(id: string): Promise<Vehicle | null> {
+    const query = 'SELECT * FROM vehicles WHERE id = $1';
+    const result = await this.pool.query(query, [id]);
+    
+    if (result.rows.length === 0) {
+      return null;
+    }
+    
+    return this.mapRow(result.rows[0]);
+  }
+
+  async findByUserAndVIN(userId: string, vin: string): Promise<Vehicle | null> {
+    const query = 'SELECT * FROM vehicles WHERE user_id = $1 AND vin = $2';
+    const result = await this.pool.query(query, [userId, vin]);
+    
+    if (result.rows.length === 0) {
+      return null;
+    }
+    
+    return this.mapRow(result.rows[0]);
+  }
+
+  async update(id: string, data: Partial<Vehicle>): Promise<Vehicle | null> {
+    const fields = [];
+    const values = [];
+    let paramCount = 1;
+
+    // Build dynamic update query
+    if (data.nickname !== undefined) {
+      fields.push(`nickname = $${paramCount++}`);
+      values.push(data.nickname);
+    }
+    if (data.color !== undefined) {
+      fields.push(`color = $${paramCount++}`);
+      values.push(data.color);
+    }
+    if (data.licensePlate !== undefined) {
+      fields.push(`license_plate = $${paramCount++}`);
+      values.push(data.licensePlate);
+    }
+    if (data.odometerReading !== undefined) {
+      fields.push(`odometer_reading = $${paramCount++}`);
+      values.push(data.odometerReading);
+    }
+
+    if (fields.length === 0) {
+      return this.findById(id);
+    }
+
+    values.push(id);
+    const query = `
+      UPDATE vehicles
+      SET ${fields.join(', ')}
+      WHERE id = $${paramCount}
+      RETURNING *
+    `;
+
+    const result = await this.pool.query(query, values);
+    
+    if (result.rows.length === 0) {
+      return null;
+    }
+    
+    return this.mapRow(result.rows[0]);
+  }
+
+  async softDelete(id: string): Promise<boolean> {
+    const query = `
+      UPDATE vehicles
+      SET is_active = false, deleted_at = NOW()
+      WHERE id = $1
+    `;
+    
+    const result = await this.pool.query(query, [id]);
+    return (result.rowCount ?? 0) > 0;
+  }
+
+  // Cache VIN decode results
+  async cacheVINDecode(vin: string, data: any): Promise<void> {
+    const query = `
+      INSERT INTO vin_cache (vin, make, model, year, engine_type, body_type, raw_data)
+      VALUES ($1, $2, $3, $4, $5, $6, $7)
+      ON CONFLICT (vin) DO UPDATE
+      SET make = $2, model = $3, year = $4, 
+          engine_type = $5, body_type = $6, raw_data = $7,
+          cached_at = NOW()
+    `;
+    
+    await this.pool.query(query, [
+      vin,
+      data.make,
+      data.model,
+      data.year,
+      data.engineType,
+      data.bodyType,
+      JSON.stringify(data.rawData)
+    ]);
+  }
+
+  async getVINFromCache(vin: string): Promise<any | null> {
+    const query = 'SELECT * FROM vin_cache WHERE vin = $1';
+    const result = await this.pool.query(query, [vin]);
+    
+    if (result.rows.length === 0) {
+      return null;
+    }
+    
+    return result.rows[0];
+  }
+
+  private mapRow(row: any): Vehicle {
+    return {
+      id: row.id,
+      userId: row.user_id,
+      vin: row.vin,
+      make: row.make,
+      model: row.model,
+      year: row.year,
+      nickname: row.nickname,
+      color: row.color,
+      licensePlate: row.license_plate,
+      odometerReading: row.odometer_reading,
+      isActive: row.is_active,
+      deletedAt: row.deleted_at,
+      createdAt: row.created_at,
+      updatedAt: row.updated_at,
+    };
+  }
+}
\ No newline at end of file