diff --git a/pkg/captcha/db.go b/pkg/captcha/db.go
index 1bca24b..a50e81c 100644
--- a/pkg/captcha/db.go
+++ b/pkg/captcha/db.go
@@ -12,7 +12,7 @@ import (
 
 var errorNotFound = errors.New("captcha not found")
 
-var expiredScanInterval = 60 * time.Second
+var defaultExpiredScanInterval = 60 * time.Second
 
 type ID string
 
@@ -29,19 +29,36 @@ func NewID(additionalData string, answer Answer) ID {
 }
 
 type CaptchaDB interface {
-	New(data string) (Captcha, ID)
-	SetExpiry(expiry time.Duration)
+	New(data string, captcha Captcha) (Captcha, ID)
 	GetExpiry() time.Duration
-	Image(id ID) (*image.Image, error)
+	Image(id ID, style string) (*image.Image, error)
 	Solve(id ID, answer Answer) (bool, error)
-	IsSolved(id ID) bool
+	IsSolved(id ID) (bool, error)
+	cleanExpired()
 }
 
 type InMemoryCaptchaDB struct {
 	sync.Mutex
 
-	DB       map[ID]Captcha
-	ExpireIn time.Duration
+	db                 map[ID]Captcha
+	expireIn           time.Duration
+	expireScanInterval time.Duration
+}
+
+func NewInMemoryCaptchaDB(expire time.Duration) *InMemoryCaptchaDB {
+	db := &InMemoryCaptchaDB{
+		db:       make(map[ID]Captcha),
+		expireIn: expire}
+
+	if expire < defaultExpiredScanInterval {
+		db.expireScanInterval = expire
+	} else {
+		db.expireScanInterval = defaultExpiredScanInterval
+	}
+
+	db.cleanExpired()
+
+	return db
 }
 
 // New accepts an Captcha instance, generates an ID and store it in a database.
@@ -51,29 +68,23 @@ func (cdb *InMemoryCaptchaDB) New(data string, captcha Captcha) (Captcha, ID) {
 	id := NewID(data, captcha.GetAnswer())
 
 	cdb.Lock()
-	cdb.DB[id] = captcha
+	cdb.db[id] = captcha
 	cdb.Unlock()
 
 	return captcha, id
 }
 
-// SetExpiry stores expire value and starts a goroutine
-// that checks for expired CAPTCHAs.
-func (cdb *InMemoryCaptchaDB) SetExpiry(expire time.Duration) {
-	cdb.ExpireIn = expire
-	if expire < expiredScanInterval {
-		expiredScanInterval = expire
-	}
-
+// cleanExpired starts a goroutine that deletes expired CAPTCHAs.
+func (cdb *InMemoryCaptchaDB) cleanExpired() {
 	go func() {
 		for {
-			sleepFor := expiredScanInterval - (time.Duration(time.Now().Second()) % expiredScanInterval)
+			sleepFor := cdb.expireScanInterval - (time.Duration(time.Now().Second()) % cdb.expireScanInterval)
 			time.Sleep(sleepFor)
 
 			cdb.Lock()
-			for id, captcha := range cdb.DB {
-				if time.Since(captcha.Expiry()) >= cdb.ExpireIn {
-					delete(cdb.DB, id)
+			for id, captcha := range cdb.db {
+				if time.Since(captcha.Expiry()) >= cdb.expireIn {
+					delete(cdb.db, id)
 				}
 			}
 			cdb.Unlock()
@@ -83,14 +94,14 @@ func (cdb *InMemoryCaptchaDB) SetExpiry(expire time.Duration) {
 
 // GetExpiry returns time for how long captcha will last.
 func (cdb *InMemoryCaptchaDB) GetExpiry() time.Duration {
-	return cdb.ExpireIn
+	return cdb.expireIn
 }
 
 // Image returns image for a captcha.
 func (cdb *InMemoryCaptchaDB) Image(id ID, style string) (*image.Image, error) {
 	cdb.Lock()
 	defer cdb.Unlock()
-	if c, ok := cdb.DB[id]; ok {
+	if c, ok := cdb.db[id]; ok {
 		return c.Image(style), nil
 	}
 	return nil, errorNotFound
@@ -101,10 +112,10 @@ func (cdb *InMemoryCaptchaDB) Image(id ID, style string) (*image.Image, error) {
 func (cdb *InMemoryCaptchaDB) Solve(id ID, answer Answer) (bool, error) {
 	cdb.Lock()
 	defer cdb.Unlock()
-	if c, ok := cdb.DB[id]; ok {
+	if c, ok := cdb.db[id]; ok {
 		ok = c.Solve(answer)
 		if !ok {
-			delete(cdb.DB, id)
+			delete(cdb.db, id)
 		}
 		return ok, nil
 	}
@@ -116,9 +127,9 @@ func (cdb *InMemoryCaptchaDB) Solve(id ID, answer Answer) (bool, error) {
 func (cdb *InMemoryCaptchaDB) IsSolved(id ID) (bool, error) {
 	cdb.Lock()
 	defer cdb.Unlock()
-	if c, ok := cdb.DB[id]; ok {
+	if c, ok := cdb.db[id]; ok {
 		ok = c.IsSolved()
-		delete(cdb.DB, id)
+		delete(cdb.db, id)
 		return ok, nil
 	}
 	return false, errorNotFound