diff --git a/cmd/user/main.go b/cmd/user/main.go
new file mode 100644
index 0000000..4f3ac4a
--- /dev/null
+++ b/cmd/user/main.go
@@ -0,0 +1,32 @@
+package main
+
+import (
+	"log"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"datarush/internal/user/config"
+	"datarush/internal/user/server"
+)
+
+func main() {
+	cfg, err := config.Load()
+	if err != nil {
+		log.Fatalf("failed to load config: %v", err)
+	}
+
+	srv := server.New(cfg)
+
+	if err := srv.Start(); err != nil {
+		log.Fatalf("failed to start server: %v", err)
+	}
+
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
+	<-quit
+
+	log.Println("shutting down user server...")
+	srv.Stop()
+	log.Println("user server stopped")
+}
\ No newline at end of file
diff --git a/internal/user/config/config.go b/internal/user/config/config.go
new file mode 100644
index 0000000..6b7ea01
--- /dev/null
+++ b/internal/user/config/config.go
@@ -0,0 +1,76 @@
+package config
+
+import (
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"strconv"
+
+	"github.com/joho/godotenv"
+)
+
+type Config struct {
+	GRPCPort             int
+	GRPCEnableReflection bool
+	HTTPPort             int
+	LogLevel             string
+	DBHost               string
+	DBPort               int
+	DBUser               string
+	DBPassword           string
+	DBName               string
+	JWTSecret            string
+}
+
+func Load() (*Config, error) {
+	_ = godotenv.Load()
+
+	return &Config{
+		GRPCPort:             mustGetInt("USER_GRPC_PORT", 50054),
+		GRPCEnableReflection: mustGetBool("USER_GRPC_ENABLE_REFLECTION", false),
+		HTTPPort:             mustGetInt("USER_HTTP_PORT", 8083),
+		LogLevel:             getEnv("LOG_LEVEL", "info"),
+		DBHost:               getEnv("POSTGRES_HOST", "localhost"),
+		DBPort:               mustGetInt("POSTGRES_PORT", 5432),
+		DBUser:               getEnv("POSTGRES_USERNAME", "postgres"),
+		DBPassword:           getEnv("POSTGRES_PASSWORD", "postgres"),
+		DBName:               getEnv("POSTGRES_DATABASE", "postgres"),
+		JWTSecret:            getEnv("JWT_SECRET", "your-secret-key-change-in-production"),
+	}, nil
+}
+
+func getEnv(key, def string) string {
+	if val := os.Getenv(key); val != "" {
+		return val
+	}
+	return def
+}
+
+func mustGetInt(key string, def int) int {
+	val := getEnv(key, strconv.Itoa(def))
+	n, err := strconv.Atoi(val)
+	if err != nil {
+		log.Fatalf("invalid int for %s: %v", key, err)
+	}
+	return n
+}
+
+func mustGetBool(key string, def bool) bool {
+	val := getEnv(key, strconv.FormatBool(def))
+	b, err := strconv.ParseBool(val)
+	if err != nil {
+		log.Fatalf("invalid bool for %s: %v", key, err)
+	}
+	return b
+}
+
+func (c Config) BuildPostgresConnStr() string {
+	return fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s sslmode=disable",
+		c.DBHost, c.DBPort, c.DBUser, c.DBPassword, c.DBName)
+}
+
+func (c Config) BuildPostgresDSN() string {
+	return fmt.Sprintf("postgresql://%s:%s@%s/%s?sslmode=disable",
+		c.DBUser, c.DBPassword, net.JoinHostPort(c.DBHost, strconv.Itoa(c.DBPort)), c.DBName)
+}
\ No newline at end of file
diff --git a/internal/user/handler/grpc/handler.go b/internal/user/handler/grpc/handler.go
new file mode 100644
index 0000000..7b4a915
--- /dev/null
+++ b/internal/user/handler/grpc/handler.go
@@ -0,0 +1,40 @@
+package grpc
+
+import (
+	"context"
+
+	pb "datarush/pkg/api/user"
+	"google.golang.org/protobuf/types/known/emptypb"
+)
+
+type UserService interface {
+	GetProfile(ctx context.Context, req *pb.GetProfileRequest) (*pb.User, error)
+	RegisterForCompetition(ctx context.Context, req *pb.RegisterForCompetitionRequest) (*emptypb.Empty, error)
+	UnregisterFromCompetition(ctx context.Context, req *pb.UnregisterFromCompetitionRequest) (*emptypb.Empty, error)
+	ListUserCompetitions(ctx context.Context, req *pb.ListUserCompetitionsRequest) (*pb.ListUserCompetitionsResponse, error)
+}
+
+type UserHandler struct {
+	pb.UnimplementedUserServiceServer
+	service UserService
+}
+
+func NewUserHandler(service UserService) *UserHandler {
+	return &UserHandler{service: service}
+}
+
+func (h *UserHandler) GetProfile(ctx context.Context, req *pb.GetProfileRequest) (*pb.User, error) {
+	return h.service.GetProfile(ctx, req)
+}
+
+func (h *UserHandler) RegisterForCompetition(ctx context.Context, req *pb.RegisterForCompetitionRequest) (*emptypb.Empty, error) {
+	return h.service.RegisterForCompetition(ctx, req)
+}
+
+func (h *UserHandler) UnregisterFromCompetition(ctx context.Context, req *pb.UnregisterFromCompetitionRequest) (*emptypb.Empty, error) {
+	return h.service.UnregisterFromCompetition(ctx, req)
+}
+
+func (h *UserHandler) ListUserCompetitions(ctx context.Context, req *pb.ListUserCompetitionsRequest) (*pb.ListUserCompetitionsResponse, error) {
+	return h.service.ListUserCompetitions(ctx, req)
+}
\ No newline at end of file
diff --git a/internal/user/middleware/auth.go b/internal/user/middleware/auth.go
new file mode 100644
index 0000000..e86be98
--- /dev/null
+++ b/internal/user/middleware/auth.go
@@ -0,0 +1,52 @@
+package middleware
+
+import (
+	"context"
+	"strings"
+
+	"github.com/golang-jwt/jwt/v5"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/status"
+)
+
+type UserIDKey struct{}
+
+func AuthInterceptor(jwtSecret string) grpc.UnaryServerInterceptor {
+	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+		md, ok := metadata.FromIncomingContext(ctx)
+		if !ok {
+			return nil, status.Errorf(codes.Unauthenticated, "metadata is not provided")
+		}
+
+		authHeader, ok := md["authorization"]
+		if !ok || len(authHeader) == 0 {
+			return nil, status.Errorf(codes.Unauthenticated, "authorization token is not provided")
+		}
+
+		tokenString := strings.TrimPrefix(authHeader[0], "Bearer ")
+
+		token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
+			if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
+				return nil, status.Errorf(codes.Unauthenticated, "unexpected signing method: %v", token.Header["alg"])
+			}
+			return []byte(jwtSecret), nil
+		})
+		if err != nil {
+			return nil, status.Errorf(codes.Unauthenticated, "invalid token: %v", err)
+		}
+
+		if claims, ok := token.Claims.(jwt.MapClaims); ok && token.Valid {
+			userID, ok := claims["user_id"].(string)
+			if !ok {
+				return nil, status.Errorf(codes.Unauthenticated, "invalid token: user_id is not a string")
+			}
+
+			newCtx := context.WithValue(ctx, UserIDKey{}, userID)
+			return handler(newCtx, req)
+		}
+
+		return nil, status.Errorf(codes.Unauthenticated, "invalid token")
+	}
+}
\ No newline at end of file
diff --git a/internal/user/repository/postgres/repository.go b/internal/user/repository/postgres/repository.go
new file mode 100644
index 0000000..a47a956
--- /dev/null
+++ b/internal/user/repository/postgres/repository.go
@@ -0,0 +1,38 @@
+package postgres
+
+import (
+	"context"
+
+	"datarush/pkg/api/user"
+	"github.com/jmoiron/sqlx"
+)
+
+type UserRepository struct {
+	db *sqlx.DB
+}
+
+func NewUserRepository(db *sqlx.DB) *UserRepository {
+	return &UserRepository{db: db}
+}
+
+func (r *UserRepository) GetProfile(ctx context.Context, userID string) (*user.User, error) {
+	var u user.User
+	err := r.db.GetContext(ctx, &u, "SELECT id, username, email, full_name, avatar_url FROM users WHERE id = $1", userID)
+	return &u, err
+}
+
+func (r *UserRepository) RegisterForCompetition(ctx context.Context, userID, competitionID string) error {
+	_, err := r.db.ExecContext(ctx, "INSERT INTO user_competitions (user_id, competition_id) VALUES ($1, $2)", userID, competitionID)
+	return err
+}
+
+func (r *UserRepository) UnregisterFromCompetition(ctx context.Context, userID, competitionID string) error {
+	_, err := r.db.ExecContext(ctx, "DELETE FROM user_competitions WHERE user_id = $1 AND competition_id = $2", userID, competitionID)
+	return err
+}
+
+func (r *UserRepository) ListUserCompetitions(ctx context.Context, userID string) ([]string, error) {
+	var competitionIDs []string
+	err := r.db.SelectContext(ctx, &competitionIDs, "SELECT competition_id FROM user_competitions WHERE user_id = $1", userID)
+	return competitionIDs, err
+}
\ No newline at end of file
diff --git a/internal/user/server/server.go b/internal/user/server/server.go
new file mode 100644
index 0000000..c945f7b
--- /dev/null
+++ b/internal/user/server/server.go
@@ -0,0 +1,99 @@
+package server
+
+import (
+	"fmt"
+	"log"
+	"net"
+	"time"
+
+	"datarush/internal/user/config"
+	grpcHandlers "datarush/internal/user/handler/grpc"
+	"datarush/internal/user/middleware"
+	userPostgresRepo "datarush/internal/user/repository/postgres"
+	"datarush/internal/user/service"
+	pb "datarush/pkg/api/user"
+
+	"github.com/jmoiron/sqlx"
+	_ "github.com/lib/pq"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/reflection"
+)
+
+const (
+	httpReadTimeout  = 10 * time.Second
+	httpWriteTimeout = 10 * time.Second
+	httpIdleTimeout  = 60 * time.Second
+)
+
+type Server struct {
+	grpcServer *grpc.Server
+	config     *config.Config
+	db         *sqlx.DB
+}
+
+func New(cfg *config.Config) *Server {
+	return &Server{
+		config: cfg,
+	}
+}
+
+func (s *Server) Start() error {
+	db, err := sqlx.Connect("postgres", s.config.BuildPostgresConnStr())
+	if err != nil {
+		return fmt.Errorf("failed to connect to postgres: %w", err)
+	}
+	s.db = db
+
+	if err := s.registerGRPCServices(); err != nil {
+		return fmt.Errorf("failed to register gRPC services: %w", err)
+	}
+
+	go func() {
+		lis, err := net.Listen("tcp", fmt.Sprintf(":%d", s.config.GRPCPort))
+		if err != nil {
+			log.Fatalf("failed to listen on grpc port: %v", err)
+		}
+
+		log.Printf("starting gRPC server on port %d", s.config.GRPCPort)
+		if err := s.grpcServer.Serve(lis); err != nil {
+			log.Fatalf("failed to serve gRPC: %v", err)
+		}
+	}()
+
+	return nil
+}
+
+func (s *Server) registerGRPCServices() error {
+	s.grpcServer = grpc.NewServer(
+		grpc.UnaryInterceptor(middleware.AuthInterceptor(s.config.JWTSecret)),
+	)
+
+	userRepo := userPostgresRepo.NewUserRepository(s.db)
+
+	userService := service.NewUserService(userRepo)
+
+	userHandler := grpcHandlers.NewUserHandler(userService)
+	pb.RegisterUserServiceServer(s.grpcServer, userHandler)
+
+	if s.config.GRPCEnableReflection {
+		reflection.Register(s.grpcServer)
+	}
+
+	return nil
+}
+
+func (s *Server) Stop() {
+	log.Println("shutting down user server...")
+
+	if s.grpcServer != nil {
+		s.grpcServer.GracefulStop()
+	}
+
+	if s.db != nil {
+		if err := s.db.Close(); err != nil {
+			log.Printf("failed to close database: %v", err)
+		}
+	}
+
+	log.Println("user server stopped")
+}
\ No newline at end of file
diff --git a/internal/user/service/mocks/mock_repository.go b/internal/user/service/mocks/mock_repository.go
new file mode 100644
index 0000000..4ca4183
--- /dev/null
+++ b/internal/user/service/mocks/mock_repository.go
@@ -0,0 +1,100 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: internal/user/service/service.go
+//
+// Generated by this command:
+//
+//	mockgen -source=internal/user/service/service.go -destination=internal/user/service/mocks/mock_repository.go -package=mocks
+//
+
+// Package mocks is a generated GoMock package.
+package mocks
+
+import (
+	context "context"
+	user "datarush/pkg/api/user"
+	reflect "reflect"
+
+	gomock "go.uber.org/mock/gomock"
+)
+
+// MockUserRepository is a mock of UserRepository interface.
+type MockUserRepository struct {
+	ctrl     *gomock.Controller
+	recorder *MockUserRepositoryMockRecorder
+	isgomock struct{}
+}
+
+// MockUserRepositoryMockRecorder is the mock recorder for MockUserRepository.
+type MockUserRepositoryMockRecorder struct {
+	mock *MockUserRepository
+}
+
+// NewMockUserRepository creates a new mock instance.
+func NewMockUserRepository(ctrl *gomock.Controller) *MockUserRepository {
+	mock := &MockUserRepository{ctrl: ctrl}
+	mock.recorder = &MockUserRepositoryMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockUserRepository) EXPECT() *MockUserRepositoryMockRecorder {
+	return m.recorder
+}
+
+// GetProfile mocks base method.
+func (m *MockUserRepository) GetProfile(ctx context.Context, userID string) (*user.User, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "GetProfile", ctx, userID)
+	ret0, _ := ret[0].(*user.User)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// GetProfile indicates an expected call of GetProfile.
+func (mr *MockUserRepositoryMockRecorder) GetProfile(ctx, userID any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetProfile", reflect.TypeOf((*MockUserRepository)(nil).GetProfile), ctx, userID)
+}
+
+// ListUserCompetitions mocks base method.
+func (m *MockUserRepository) ListUserCompetitions(ctx context.Context, userID string) ([]string, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "ListUserCompetitions", ctx, userID)
+	ret0, _ := ret[0].([]string)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// ListUserCompetitions indicates an expected call of ListUserCompetitions.
+func (mr *MockUserRepositoryMockRecorder) ListUserCompetitions(ctx, userID any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ListUserCompetitions", reflect.TypeOf((*MockUserRepository)(nil).ListUserCompetitions), ctx, userID)
+}
+
+// RegisterForCompetition mocks base method.
+func (m *MockUserRepository) RegisterForCompetition(ctx context.Context, userID, competitionID string) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "RegisterForCompetition", ctx, userID, competitionID)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// RegisterForCompetition indicates an expected call of RegisterForCompetition.
+func (mr *MockUserRepositoryMockRecorder) RegisterForCompetition(ctx, userID, competitionID any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "RegisterForCompetition", reflect.TypeOf((*MockUserRepository)(nil).RegisterForCompetition), ctx, userID, competitionID)
+}
+
+// UnregisterFromCompetition mocks base method.
+func (m *MockUserRepository) UnregisterFromCompetition(ctx context.Context, userID, competitionID string) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "UnregisterFromCompetition", ctx, userID, competitionID)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// UnregisterFromCompetition indicates an expected call of UnregisterFromCompetition.
+func (mr *MockUserRepositoryMockRecorder) UnregisterFromCompetition(ctx, userID, competitionID any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "UnregisterFromCompetition", reflect.TypeOf((*MockUserRepository)(nil).UnregisterFromCompetition), ctx, userID, competitionID)
+}
diff --git a/internal/user/service/service.go b/internal/user/service/service.go
new file mode 100644
index 0000000..5c2db7e
--- /dev/null
+++ b/internal/user/service/service.go
@@ -0,0 +1,57 @@
+package service
+
+import (
+	"context"
+	"errors"
+
+	"datarush/internal/user/middleware"
+	pb "datarush/pkg/api/user"
+	"google.golang.org/protobuf/types/known/emptypb"
+)
+
+type UserRepository interface {
+	GetProfile(ctx context.Context, userID string) (*pb.User, error)
+	RegisterForCompetition(ctx context.Context, userID, competitionID string) error
+	UnregisterFromCompetition(ctx context.Context, userID, competitionID string) error
+	ListUserCompetitions(ctx context.Context, userID string) ([]string, error)
+}
+
+type UserService struct {
+	repo UserRepository
+}
+
+func NewUserService(repo UserRepository) *UserService {
+	return &UserService{repo: repo}
+}
+
+func (s *UserService) GetProfile(ctx context.Context, req *pb.GetProfileRequest) (*pb.User, error) {
+	return s.repo.GetProfile(ctx, req.UserId)
+}
+
+func (s *UserService) RegisterForCompetition(ctx context.Context, req *pb.RegisterForCompetitionRequest) (*emptypb.Empty, error) {
+	userID, ok := ctx.Value(middleware.UserIDKey{}).(string)
+	if !ok {
+		return nil, errors.New("user ID not found in context")
+	}
+
+	err := s.repo.RegisterForCompetition(ctx, userID, req.CompetitionId)
+	return &emptypb.Empty{}, err
+}
+
+func (s *UserService) UnregisterFromCompetition(ctx context.Context, req *pb.UnregisterFromCompetitionRequest) (*emptypb.Empty, error) {
+	userID, ok := ctx.Value(middleware.UserIDKey{}).(string)
+	if !ok {
+		return nil, errors.New("user ID not found in context")
+	}
+
+	err := s.repo.UnregisterFromCompetition(ctx, userID, req.CompetitionId)
+	return &emptypb.Empty{}, err
+}
+
+func (s *UserService) ListUserCompetitions(ctx context.Context, req *pb.ListUserCompetitionsRequest) (*pb.ListUserCompetitionsResponse, error) {
+	competitionIDs, err := s.repo.ListUserCompetitions(ctx, req.UserId)
+	if err != nil {
+		return nil, err
+	}
+	return &pb.ListUserCompetitionsResponse{CompetitionIds: competitionIDs}, nil
+}
\ No newline at end of file
diff --git a/internal/user/service/service_test.go b/internal/user/service/service_test.go
new file mode 100644
index 0000000..85d4477
--- /dev/null
+++ b/internal/user/service/service_test.go
@@ -0,0 +1,102 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"datarush/internal/user/middleware"
+	"datarush/internal/user/service/mocks"
+	pb "datarush/pkg/api/user"
+
+	"go.uber.org/mock/gomock"
+	"github.com/stretchr/testify/assert"
+	"google.golang.org/protobuf/types/known/emptypb"
+)
+
+func TestUserService(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	mockRepo := mocks.NewMockUserRepository(ctrl)
+	service := NewUserService(mockRepo)
+
+	ctx := context.Background()
+	userID := "test-user-id"
+	ctx = context.WithValue(ctx, middleware.UserIDKey{}, userID)
+
+	t.Run("GetProfile", func(t *testing.T) {
+		req := &pb.GetProfileRequest{UserId: userID}
+		expectedUser := &pb.User{
+			Id:       userID,
+			Username: "testuser",
+			Email:    "test@example.com",
+		}
+
+		mockRepo.EXPECT().GetProfile(ctx, userID).Return(expectedUser, nil)
+
+		user, err := service.GetProfile(ctx, req)
+		assert.NoError(t, err)
+		assert.Equal(t, expectedUser, user)
+	})
+
+	t.Run("RegisterForCompetition", func(t *testing.T) {
+		competitionID := "comp1"
+		req := &pb.RegisterForCompetitionRequest{CompetitionId: competitionID}
+
+		mockRepo.EXPECT().RegisterForCompetition(ctx, userID, competitionID).Return(nil)
+
+		_, err := service.RegisterForCompetition(ctx, req)
+		assert.NoError(t, err)
+	})
+
+	t.Run("RegisterForCompetition - No UserID in context", func(t *testing.T) {
+		competitionID := "comp1"
+		req := &pb.RegisterForCompetitionRequest{CompetitionId: competitionID}
+
+		_, err := service.RegisterForCompetition(context.Background(), req)
+		assert.Error(t, err)
+		assert.Equal(t, "user ID not found in context", err.Error())
+	})
+
+	t.Run("UnregisterFromCompetition", func(t *testing.T) {
+		competitionID := "comp1"
+		req := &pb.UnregisterFromCompetitionRequest{CompetitionId: competitionID}
+
+		mockRepo.EXPECT().UnregisterFromCompetition(ctx, userID, competitionID).Return(nil)
+
+		_, err := service.UnregisterFromCompetition(ctx, req)
+		assert.NoError(t, err)
+	})
+
+	t.Run("UnregisterFromCompetition - No UserID in context", func(t *testing.T) {
+		competitionID := "comp1"
+		req := &pb.UnregisterFromCompetitionRequest{CompetitionId: competitionID}
+
+		_, err := service.UnregisterFromCompetition(context.Background(), req)
+		assert.Error(t, err)
+		assert.Equal(t, "user ID not found in context", err.Error())
+	})
+
+	t.Run("ListUserCompetitions", func(t *testing.T) {
+		req := &pb.ListUserCompetitionsRequest{UserId: userID}
+		expectedCompetitionIDs := []string{"comp1", "comp2"}
+
+		mockRepo.EXPECT().ListUserCompetitions(ctx, userID).Return(expectedCompetitionIDs, nil)
+
+		resp, err := service.ListUserCompetitions(ctx, req)
+		assert.NoError(t, err)
+		assert.Equal(t, expectedCompetitionIDs, resp.CompetitionIds)
+	})
+
+	t.Run("ListUserCompetitions - Error", func(t *testing.T) {
+		req := &pb.ListUserCompetitionsRequest{UserId: userID}
+		expectedError := errors.New("repository error")
+
+		mockRepo.EXPECT().ListUserCompetitions(ctx, userID).Return(nil, expectedError)
+
+		_, err := service.ListUserCompetitions(ctx, req)
+		assert.Error(t, err)
+		assert.Equal(t, expectedError, err)
+	})
+}
\ No newline at end of file