diff --git a/go.mod b/go.mod
index de1ba89..0bebfe1 100644
--- a/go.mod
+++ b/go.mod
@@ -4,7 +4,7 @@ go 1.13
 
 require (
 	github.com/gorilla/mux v1.7.3
-	github.com/mattn/go-sqlite3 v2.0.1+incompatible
+	github.com/mattn/go-sqlite3 v2.0.2+incompatible // indirect
 	mastodon v0.0.0-00010101000000-000000000000
 )
 
diff --git a/go.mod.old b/go.mod.old
new file mode 100644
index 0000000..e633126
--- /dev/null
+++ b/go.mod.old
@@ -0,0 +1,10 @@
+module web
+
+go 1.13
+
+require (
+	github.com/gorilla/mux v1.7.3
+	mastodon v0.0.0-00010101000000-000000000000
+)
+
+replace mastodon => ./mastodon
diff --git a/go.sum b/go.sum
index 236732d..7a53570 100644
--- a/go.sum
+++ b/go.sum
@@ -2,7 +2,7 @@ github.com/gorilla/mux v1.7.3 h1:gnP5JzjVOuiZD07fKKToCAOjS0yOpj/qPETTXCCS6hw=
 github.com/gorilla/mux v1.7.3/go.mod h1:1lud6UwP+6orDFRuTfBEV8e9/aOM/c4fVVCaMa2zaAs=
 github.com/gorilla/websocket v1.4.1 h1:q7AeDBpnBk8AogcD4DSag/Ukw/KV+YhzLj2bP5HvKCM=
 github.com/gorilla/websocket v1.4.1/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
-github.com/mattn/go-sqlite3 v2.0.1+incompatible h1:xQ15muvnzGBHpIpdrNi1DA5x0+TcBZzsIDwmw9uTHzw=
-github.com/mattn/go-sqlite3 v2.0.1+incompatible/go.mod h1:FPy6KqzDD04eiIsT53CuJW3U88zkxoIYsOqkbpncsNc=
+github.com/mattn/go-sqlite3 v2.0.2+incompatible h1:qzw9c2GNT8UFrgWNDhCTqRqYUSmu/Dav/9Z58LGpk7U=
+github.com/mattn/go-sqlite3 v2.0.2+incompatible/go.mod h1:FPy6KqzDD04eiIsT53CuJW3U88zkxoIYsOqkbpncsNc=
 github.com/tomnomnom/linkheader v0.0.0-20180905144013-02ca5825eb80 h1:nrZ3ySNYwJbSpD6ce9duiP+QkD3JuLCcWkdaehUS/3Y=
 github.com/tomnomnom/linkheader v0.0.0-20180905144013-02ca5825eb80/go.mod h1:iFyPdL66DjUD96XmzVL3ZntbzcflLnznH0fr99w5VqE=
diff --git a/kv/kv.go b/kv/kv.go
new file mode 100644
index 0000000..2cfcd60
--- /dev/null
+++ b/kv/kv.go
@@ -0,0 +1,92 @@
+package kv
+
+import (
+	"errors"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+)
+
+var (
+	errInvalidKey = errors.New("invalid key")
+	errNoSuchKey  = errors.New("no such key")
+)
+
+type Database struct {
+	data    map[string][]byte
+	basedir string
+	m       sync.RWMutex
+}
+
+func NewDatabse(basedir string) (db *Database, err error) {
+	err = os.Mkdir(basedir, 0755)
+	if err != nil && !os.IsExist(err) {
+		return
+	}
+
+	return &Database{
+		data:    make(map[string][]byte),
+		basedir: basedir,
+	}, nil
+}
+
+func (db *Database) Set(key string, val []byte) (err error) {
+	if len(key) < 1 {
+		return errInvalidKey
+	}
+
+	db.m.Lock()
+	defer func() {
+		if err != nil {
+			delete(db.data, key)
+		}
+		db.m.Unlock()
+	}()
+
+	db.data[key] = val
+
+	err = ioutil.WriteFile(filepath.Join(db.basedir, key), val, 0644)
+
+	return
+}
+
+func (db *Database) Get(key string) (val []byte, err error) {
+	if len(key) < 1 {
+		return nil, errInvalidKey
+	}
+
+	db.m.RLock()
+	defer db.m.RUnlock()
+
+	data, ok := db.data[key]
+	if !ok {
+		data, err = ioutil.ReadFile(filepath.Join(db.basedir, key))
+		if err != nil {
+			err = errNoSuchKey
+			return nil, err
+		}
+
+		db.data[key] = data
+	}
+
+	val = make([]byte, len(data))
+	copy(val, data)
+
+	return
+}
+
+func (db *Database) Remove(key string) {
+	if len(key) < 1 || strings.ContainsRune(key, os.PathSeparator) {
+		return
+	}
+
+	db.m.Lock()
+	defer db.m.Unlock()
+
+	delete(db.data, key)
+	os.Remove(filepath.Join(db.basedir, key))
+
+	return
+}
diff --git a/main.go b/main.go
index d726fed..ad62976 100644
--- a/main.go
+++ b/main.go
@@ -1,19 +1,18 @@
 package main
 
 import (
-	"database/sql"
 	"log"
 	"math/rand"
 	"net/http"
 	"os"
+	"path/filepath"
 	"time"
 
 	"web/config"
+	"web/kv"
 	"web/renderer"
 	"web/repository"
 	"web/service"
-
-	_ "github.com/mattn/go-sqlite3"
 )
 
 func init() {
@@ -35,22 +34,24 @@ func main() {
 		log.Fatal(err)
 	}
 
-	db, err := sql.Open("sqlite3", config.DatabasePath)
-	if err != nil {
+	err = os.Mkdir(config.DatabasePath, 0755)
+	if err != nil && !os.IsExist(err) {
 		log.Fatal(err)
 	}
-	defer db.Close()
 
-	sessionRepo, err := repository.NewSessionRepository(db)
+	sessionDB, err := kv.NewDatabse(filepath.Join(config.DatabasePath, "session"))
 	if err != nil {
 		log.Fatal(err)
 	}
 
-	appRepo, err := repository.NewAppRepository(db)
+	appDB, err := kv.NewDatabse(filepath.Join(config.DatabasePath, "app"))
 	if err != nil {
 		log.Fatal(err)
 	}
 
+	sessionRepo := repository.NewSessionRepository(sessionDB)
+	appRepo := repository.NewAppRepository(appDB)
+
 	var logger *log.Logger
 	if len(config.Logfile) < 1 {
 		logger = log.New(os.Stdout, "", log.LstdFlags)
diff --git a/model/app.go b/model/app.go
index 52ebdf5..89d656d 100644
--- a/model/app.go
+++ b/model/app.go
@@ -1,19 +1,40 @@
 package model
 
-import "errors"
+import (
+	"errors"
+	"strings"
+)
 
 var (
 	ErrAppNotFound = errors.New("app not found")
 )
 
 type App struct {
-	InstanceURL  string
-	ClientID     string
-	ClientSecret string
+	InstanceDomain string
+	InstanceURL    string
+	ClientID       string
+	ClientSecret   string
 }
 
 type AppRepository interface {
 	Add(app App) (err error)
-	Update(instanceURL string, clientID string, clientSecret string) (err error)
-	Get(instanceURL string) (app App, err error)
+	Get(instanceDomain string) (app App, err error)
+}
+
+func (a *App) Marshal() []byte {
+	str := a.InstanceURL + "\n" + a.ClientID + "\n" + a.ClientSecret
+	return []byte(str)
+}
+
+func (a *App) Unmarshal(instanceDomain string, data []byte) error {
+	str := string(data)
+	lines := strings.Split(str, "\n")
+	if len(lines) != 3 {
+		return errors.New("invalid data")
+	}
+	a.InstanceDomain = instanceDomain
+	a.InstanceURL = lines[0]
+	a.ClientID = lines[1]
+	a.ClientSecret = lines[2]
+	return nil
 }
diff --git a/model/session.go b/model/session.go
index 43628ee..94f527b 100644
--- a/model/session.go
+++ b/model/session.go
@@ -1,15 +1,18 @@
 package model
 
-import "errors"
+import (
+	"errors"
+	"strings"
+)
 
 var (
 	ErrSessionNotFound = errors.New("session not found")
 )
 
 type Session struct {
-	ID          string
-	InstanceURL string
-	AccessToken string
+	ID             string
+	InstanceDomain string
+	AccessToken    string
 }
 
 type SessionRepository interface {
@@ -21,3 +24,26 @@ type SessionRepository interface {
 func (s Session) IsLoggedIn() bool {
 	return len(s.AccessToken) > 0
 }
+
+func (s *Session) Marshal() []byte {
+	str := s.InstanceDomain + "\n" + s.AccessToken
+	return []byte(str)
+}
+
+func (s *Session) Unmarshal(id string, data []byte) error {
+	str := string(data)
+	lines := strings.Split(str, "\n")
+
+	size := len(lines)
+	if size == 1 {
+		s.InstanceDomain = lines[0]
+	} else if size == 2 {
+		s.InstanceDomain = lines[0]
+		s.AccessToken = lines[1]
+	} else {
+		return errors.New("invalid data")
+	}
+
+	s.ID = id
+	return nil
+}
diff --git a/repository/appRepository.go b/repository/appRepository.go
index 1a8f204..00ef64d 100644
--- a/repository/appRepository.go
+++ b/repository/appRepository.go
@@ -1,54 +1,33 @@
 package repository
 
 import (
-	"database/sql"
-
+	"web/kv"
 	"web/model"
 )
 
 type appRepository struct {
-	db *sql.DB
+	db *kv.Database
 }
 
-func NewAppRepository(db *sql.DB) (*appRepository, error) {
-	_, err := db.Exec(`CREATE TABLE IF NOT EXISTS app 
-		(instance_url varchar, client_id varchar, client_secret varchar)`,
-	)
-	if err != nil {
-		return nil, err
-	}
-
+func NewAppRepository(db *kv.Database) *appRepository {
 	return &appRepository{
 		db: db,
-	}, nil
+	}
 }
 
 func (repo *appRepository) Add(a model.App) (err error) {
-	_, err = repo.db.Exec("INSERT INTO app VALUES (?, ?, ?)", a.InstanceURL, a.ClientID, a.ClientSecret)
+	err = repo.db.Set(a.InstanceDomain, a.Marshal())
 	return
 }
 
-func (repo *appRepository) Update(instanceURL string, clientID string, clientSecret string) (err error) {
-	_, err = repo.db.Exec("UPDATE app SET client_id = ?, client_secret = ? where instance_url = ?", clientID, clientSecret, instanceURL)
-	return
-}
-
-func (repo *appRepository) Get(instanceURL string) (a model.App, err error) {
-	rows, err := repo.db.Query("SELECT * FROM app WHERE instance_url = ?", instanceURL)
+func (repo *appRepository) Get(instanceDomain string) (a model.App, err error) {
+	data, err := repo.db.Get(instanceDomain)
 	if err != nil {
-		return
-	}
-	defer rows.Close()
-
-	if !rows.Next() {
 		err = model.ErrAppNotFound
 		return
 	}
 
-	err = rows.Scan(&a.InstanceURL, &a.ClientID, &a.ClientSecret)
-	if err != nil {
-		return
-	}
+	err = a.Unmarshal(instanceDomain, data)
 
 	return
 }
diff --git a/repository/sessionRepository.go b/repository/sessionRepository.go
index 2a88b40..6c26313 100644
--- a/repository/sessionRepository.go
+++ b/repository/sessionRepository.go
@@ -1,54 +1,50 @@
 package repository
 
 import (
-	"database/sql"
-
+	"web/kv"
 	"web/model"
 )
 
 type sessionRepository struct {
-	db *sql.DB
+	db *kv.Database
 }
 
-func NewSessionRepository(db *sql.DB) (*sessionRepository, error) {
-	_, err := db.Exec(`CREATE TABLE IF NOT EXISTS session 
-		(id varchar, instance_url varchar, access_token varchar)`,
-	)
-	if err != nil {
-		return nil, err
-	}
-
+func NewSessionRepository(db *kv.Database) *sessionRepository {
 	return &sessionRepository{
 		db: db,
-	}, nil
+	}
 }
 
 func (repo *sessionRepository) Add(s model.Session) (err error) {
-	_, err = repo.db.Exec("INSERT INTO session VALUES (?, ?, ?)", s.ID, s.InstanceURL, s.AccessToken)
+	err = repo.db.Set(s.ID, s.Marshal())
 	return
 }
 
-func (repo *sessionRepository) Update(sessionID string, accessToken string) (err error) {
-	_, err = repo.db.Exec("UPDATE session SET access_token = ? where id = ?", accessToken, sessionID)
-	return
-}
-
-func (repo *sessionRepository) Get(id string) (s model.Session, err error) {
-	rows, err := repo.db.Query("SELECT * FROM session WHERE id = ?", id)
+func (repo *sessionRepository) Update(id string, accessToken string) (err error) {
+	data, err := repo.db.Get(id)
 	if err != nil {
 		return
 	}
-	defer rows.Close()
 
-	if !rows.Next() {
+	var s model.Session
+	err = s.Unmarshal(id, data)
+	if err != nil {
+		return
+	}
+
+	s.AccessToken = accessToken
+
+	return repo.db.Set(id, s.Marshal())
+}
+
+func (repo *sessionRepository) Get(id string) (s model.Session, err error) {
+	data, err := repo.db.Get(id)
+	if err != nil {
 		err = model.ErrSessionNotFound
 		return
 	}
 
-	err = rows.Scan(&s.ID, &s.InstanceURL, &s.AccessToken)
-	if err != nil {
-		return
-	}
+	err = s.Unmarshal(id, data)
 
 	return
 }
diff --git a/service/auth.go b/service/auth.go
index e9bec38..38c0a43 100644
--- a/service/auth.go
+++ b/service/auth.go
@@ -40,12 +40,12 @@ func (s *authService) getClient(ctx context.Context) (c *mastodon.Client, err er
 	if err != nil {
 		return nil, ErrInvalidSession
 	}
-	client, err := s.appRepo.Get(session.InstanceURL)
+	client, err := s.appRepo.Get(session.InstanceDomain)
 	if err != nil {
 		return
 	}
 	c = mastodon.NewClient(&mastodon.Config{
-		Server:       session.InstanceURL,
+		Server:       client.InstanceURL,
 		ClientID:     client.ClientID,
 		ClientSecret: client.ClientSecret,
 		AccessToken:  session.AccessToken,
diff --git a/service/service.go b/service/service.go
index 5181475..bb03c26 100644
--- a/service/service.go
+++ b/service/service.go
@@ -9,7 +9,6 @@ import (
 	"mime/multipart"
 	"net/http"
 	"net/url"
-	"path"
 	"strings"
 
 	"mastodon"
@@ -64,14 +63,18 @@ func NewService(clientName string, clientScope string, clientWebsite string,
 
 func (svc *service) GetAuthUrl(ctx context.Context, instance string) (
 	redirectUrl string, sessionID string, err error) {
-	if !strings.HasPrefix(instance, "https://") {
-		instance = "https://" + instance
+	var instanceURL string
+	if strings.HasPrefix(instance, "https://") {
+		instanceURL = instance
+		instance = strings.TrimPrefix(instance, "https://")
+	} else {
+		instanceURL = "https://" + instance
 	}
 
 	sessionID = util.NewSessionId()
 	err = svc.sessionRepo.Add(model.Session{
-		ID:          sessionID,
-		InstanceURL: instance,
+		ID:             sessionID,
+		InstanceDomain: instance,
 	})
 	if err != nil {
 		return
@@ -85,7 +88,7 @@ func (svc *service) GetAuthUrl(ctx context.Context, instance string) (
 
 		var mastoApp *mastodon.Application
 		mastoApp, err = mastodon.RegisterApp(ctx, &mastodon.AppConfig{
-			Server:       instance,
+			Server:       instanceURL,
 			ClientName:   svc.clientName,
 			Scopes:       svc.clientScope,
 			Website:      svc.clientWebsite,
@@ -96,9 +99,10 @@ func (svc *service) GetAuthUrl(ctx context.Context, instance string) (
 		}
 
 		app = model.App{
-			InstanceURL:  instance,
-			ClientID:     mastoApp.ClientID,
-			ClientSecret: mastoApp.ClientSecret,
+			InstanceDomain: instance,
+			InstanceURL:    instanceURL,
+			ClientID:       mastoApp.ClientID,
+			ClientSecret:   mastoApp.ClientSecret,
 		}
 
 		err = svc.appRepo.Add(app)
@@ -136,7 +140,7 @@ func (svc *service) GetUserToken(ctx context.Context, sessionID string, c *masto
 		return
 	}
 
-	app, err := svc.appRepo.Get(session.InstanceURL)
+	app, err := svc.appRepo.Get(session.InstanceDomain)
 	if err != nil {
 		return
 	}