diff --git a/briar-api/src/main/java/org/briarproject/briar/api/introduction/IntroductionManager.java b/briar-api/src/main/java/org/briarproject/briar/api/introduction/IntroductionManager.java
index 84b4b3028..a3bc6f007 100644
--- a/briar-api/src/main/java/org/briarproject/briar/api/introduction/IntroductionManager.java
+++ b/briar-api/src/main/java/org/briarproject/briar/api/introduction/IntroductionManager.java
@@ -29,6 +29,12 @@ public interface IntroductionManager extends ConversationClient {
 	 */
 	boolean canIntroduce(Contact c1, Contact c2) throws DbException;
 
+	/**
+	 * Returns true if both contacts can be introduced at this moment.
+	 */
+	boolean canIntroduce(Transaction txn, Contact c1, Contact c2)
+			throws DbException;
+
 	/**
 	 * The current minor version of the introduction client.
 	 */
@@ -40,6 +46,12 @@ public interface IntroductionManager extends ConversationClient {
 	void makeIntroduction(Contact c1, Contact c2, @Nullable String text)
 			throws DbException;
 
+	/**
+	 * Sends two initial introduction messages.
+	 */
+	void makeIntroduction(Transaction txn, Contact c1, Contact c2,
+			@Nullable String text) throws DbException;
+
 	/**
 	 * Responds to an introduction.
 	 */
diff --git a/briar-api/src/main/java/org/briarproject/briar/api/privategroup/PrivateGroupManager.java b/briar-api/src/main/java/org/briarproject/briar/api/privategroup/PrivateGroupManager.java
index ceeb8d9c6..756231bd8 100644
--- a/briar-api/src/main/java/org/briarproject/briar/api/privategroup/PrivateGroupManager.java
+++ b/briar-api/src/main/java/org/briarproject/briar/api/privategroup/PrivateGroupManager.java
@@ -52,11 +52,21 @@ public interface PrivateGroupManager {
 	void addPrivateGroup(Transaction txn, PrivateGroup group,
 			GroupMessage joinMsg, boolean creator) throws DbException;
 
+	/**
+	 * Removes a dissolved private group.
+	 */
+	void removePrivateGroup(Transaction txn, GroupId g) throws DbException;
+
 	/**
 	 * Removes a dissolved private group.
 	 */
 	void removePrivateGroup(GroupId g) throws DbException;
 
+	/**
+	 * Returns the ID of the user's previous message sent to the group
+	 */
+	MessageId getPreviousMsgId(Transaction txn, GroupId g) throws DbException;
+
 	/**
 	 * Returns the ID of the user's previous message sent to the group
 	 */
@@ -112,7 +122,8 @@ public interface PrivateGroupManager {
 	/**
 	 * Returns true if the given private group was created by us.
 	 */
-	boolean isOurPrivateGroup(Transaction txn, PrivateGroup g) throws DbException;
+	boolean isOurPrivateGroup(Transaction txn, PrivateGroup g)
+			throws DbException;
 
 	/**
 	 * Returns the text of the private group message with the given ID.
@@ -161,6 +172,12 @@ public interface PrivateGroupManager {
 	 */
 	GroupCount getGroupCount(GroupId g) throws DbException;
 
+	/**
+	 * Marks a message as read or unread and updates the group count.
+	 */
+	void setReadFlag(Transaction txn, GroupId g, MessageId m, boolean read)
+			throws DbException;
+
 	/**
 	 * Marks a message as read or unread and updates the group count.
 	 */
diff --git a/briar-core/src/main/java/org/briarproject/briar/introduction/IntroductionManagerImpl.java b/briar-core/src/main/java/org/briarproject/briar/introduction/IntroductionManagerImpl.java
index b3b1a6077..e3bfb9943 100644
--- a/briar-core/src/main/java/org/briarproject/briar/introduction/IntroductionManagerImpl.java
+++ b/briar-core/src/main/java/org/briarproject/briar/introduction/IntroductionManagerImpl.java
@@ -300,36 +300,37 @@ class IntroductionManagerImpl extends ConversationClientImpl
 
 	@Override
 	public boolean canIntroduce(Contact c1, Contact c2) throws DbException {
-		Transaction txn = db.startTransaction(true);
+		return db.transactionWithResult(true,
+				txn -> canIntroduce(txn, c1, c2));
+	}
+
+	public boolean canIntroduce(Transaction txn, Contact c1, Contact c2)
+			throws DbException {
 		try {
-			boolean can = canIntroduce(txn, c1, c2);
-			db.commitTransaction(txn);
-			return can;
+			// Look up the session, if there is one
+			Author introducer = identityManager.getLocalAuthor(txn);
+			SessionId sessionId =
+					crypto.getSessionId(introducer, c1.getAuthor(),
+							c2.getAuthor());
+			StoredSession ss = getSession(txn, sessionId);
+			if (ss == null) return true;
+			IntroducerSession session =
+					sessionParser.parseIntroducerSession(ss.bdfSession);
+			return session.getState().isComplete();
 		} catch (FormatException e) {
 			throw new DbException(e);
-		} finally {
-			db.endTransaction(txn);
 		}
 	}
 
-	private boolean canIntroduce(Transaction txn, Contact c1, Contact c2)
-			throws DbException, FormatException {
-		// Look up the session, if there is one
-		Author introducer = identityManager.getLocalAuthor(txn);
-		SessionId sessionId =
-				crypto.getSessionId(introducer, c1.getAuthor(),
-						c2.getAuthor());
-		StoredSession ss = getSession(txn, sessionId);
-		if (ss == null) return true;
-		IntroducerSession session =
-				sessionParser.parseIntroducerSession(ss.bdfSession);
-		return session.getState().isComplete();
+	public void makeIntroduction(Contact c1, Contact c2, @Nullable String text)
+			throws DbException {
+		db.transaction(false,
+				txn -> makeIntroduction(txn, c1, c2, text));
 	}
 
 	@Override
-	public void makeIntroduction(Contact c1, Contact c2, @Nullable String text)
-			throws DbException {
-		Transaction txn = db.startTransaction(false);
+	public void makeIntroduction(Transaction txn, Contact c1, Contact c2,
+			@Nullable String text) throws DbException {
 		try {
 			// Look up the session, if there is one
 			Author introducer = identityManager.getLocalAuthor(txn);
@@ -363,11 +364,8 @@ class IntroductionManagerImpl extends ConversationClientImpl
 			session = introducerEngine.onRequestAction(txn, session, text);
 			// Store the updated session
 			storeSession(txn, storageId, session);
-			db.commitTransaction(txn);
 		} catch (FormatException e) {
 			throw new DbException(e);
-		} finally {
-			db.endTransaction(txn);
 		}
 	}
 
diff --git a/briar-core/src/main/java/org/briarproject/briar/privategroup/PrivateGroupManagerImpl.java b/briar-core/src/main/java/org/briarproject/briar/privategroup/PrivateGroupManagerImpl.java
index 088cbc4ce..1e06214ca 100644
--- a/briar-core/src/main/java/org/briarproject/briar/privategroup/PrivateGroupManagerImpl.java
+++ b/briar-core/src/main/java/org/briarproject/briar/privategroup/PrivateGroupManagerImpl.java
@@ -150,40 +150,35 @@ class PrivateGroupManagerImpl extends BdfIncomingMessageHook
 	}
 
 	@Override
-	public void removePrivateGroup(GroupId g) throws DbException {
-		Transaction txn = db.startTransaction(false);
-		try {
-			for (PrivateGroupHook hook : hooks) {
-				hook.removingGroup(txn, g);
-			}
-			Group group = db.getGroup(txn, g);
-			db.removeGroup(txn, group);
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
+	public void removePrivateGroup(Transaction txn, GroupId g)
+			throws DbException {
+		for (PrivateGroupHook hook : hooks) {
+			hook.removingGroup(txn, g);
 		}
+		Group group = db.getGroup(txn, g);
+		db.removeGroup(txn, group);
+	}
+
+	@Override
+	public void removePrivateGroup(GroupId g) throws DbException {
+		db.transaction(false, txn -> removePrivateGroup(txn, g));
 	}
 
 	@Override
 	public MessageId getPreviousMsgId(GroupId g) throws DbException {
-		MessageId previousMsgId;
-		Transaction txn = db.startTransaction(true);
-		try {
-			previousMsgId = getPreviousMsgId(txn, g);
-			db.commitTransaction(txn);
-		} catch (FormatException e) {
-			throw new DbException(e);
-		} finally {
-			db.endTransaction(txn);
-		}
-		return previousMsgId;
+		return db.transactionWithResult(true,
+				txn -> getPreviousMsgId(txn, g));
 	}
 
-	private MessageId getPreviousMsgId(Transaction txn, GroupId g)
-			throws DbException, FormatException {
-		BdfDictionary d = clientHelper.getGroupMetadataAsDictionary(txn, g);
-		byte[] previousMsgIdBytes = d.getRaw(KEY_PREVIOUS_MSG_ID);
-		return new MessageId(previousMsgIdBytes);
+	public MessageId getPreviousMsgId(Transaction txn, GroupId g)
+			throws DbException {
+		try {
+			BdfDictionary d = clientHelper.getGroupMetadataAsDictionary(txn, g);
+			byte[] previousMsgIdBytes = d.getRaw(KEY_PREVIOUS_MSG_ID);
+			return new MessageId(previousMsgIdBytes);
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
 	}
 
 	private void setPreviousMsgId(Transaction txn, GroupId g,
@@ -483,11 +478,16 @@ class PrivateGroupManagerImpl extends BdfIncomingMessageHook
 		return messageTracker.getGroupCount(g);
 	}
 
+	@Override
+	public void setReadFlag(Transaction txn, GroupId g, MessageId m,
+			boolean read) throws DbException {
+		messageTracker.setReadFlag(txn, g, m, read);
+	}
+
 	@Override
 	public void setReadFlag(GroupId g, MessageId m, boolean read)
 			throws DbException {
-		db.transaction(false, txn ->
-				messageTracker.setReadFlag(txn, g, m, read));
+		db.transaction(false, txn -> setReadFlag(txn, g, m, read));
 	}
 
 	@Override