diff --git a/src/main/java/org/qora/account/Account.java b/src/main/java/org/qora/account/Account.java
index 50da8c7b..dacb8c9e 100644
--- a/src/main/java/org/qora/account/Account.java
+++ b/src/main/java/org/qora/account/Account.java
@@ -163,36 +163,18 @@ public class Account {
 	}
 
 	/**
-	 * Fetch last reference for account, considering unconfirmed transactions.
+	 * Fetch last reference for account, considering unconfirmed transactions only, or return null.
 	 * <p>
 	 * NOTE: a repository savepoint may be used during execution.
 	 * 
-	 * @return byte[] reference, or null if no reference or account not found.
+	 * @return byte[] reference, or null if no unconfirmed transactions for this account.
 	 * @throws DataException
 	 */
 	public byte[] getUnconfirmedLastReference() throws DataException {
-		byte[] reference = getUnconfirmedLastReference(null);
-
-		if (reference == null)
-			// No unconfirmed transactions
-			reference = getLastReference();
-
-		return reference;
-	}
-
-	/**
-	 * Fetch last reference for account, considering unconfirmed transactions only, or return defaultReference.
-	 * <p>
-	 * NOTE: a repository savepoint may be used during execution.
-	 * 
-	 * @return byte[] reference, or defaultReference if no unconfirmed transactions for this account.
-	 * @throws DataException
-	 */
-	public byte[] getUnconfirmedLastReference(byte[] defaultReference) throws DataException {
 		// Newest unconfirmed transaction takes priority
 		List<TransactionData> unconfirmedTransactions = Transaction.getUnconfirmedTransactions(repository);
 
-		byte[] reference = defaultReference;
+		byte[] reference = null;
 
 		for (TransactionData transactionData : unconfirmedTransactions) {
 			String address = PublicKeyAccount.getAddress(transactionData.getCreatorPublicKey());
diff --git a/src/main/java/org/qora/api/resource/AddressesResource.java b/src/main/java/org/qora/api/resource/AddressesResource.java
index 4d3f4dc8..dc42e6ff 100644
--- a/src/main/java/org/qora/api/resource/AddressesResource.java
+++ b/src/main/java/org/qora/api/resource/AddressesResource.java
@@ -78,7 +78,7 @@ public class AddressesResource {
 			else {
 				// Unconfirmed transactions could update lastReference
 				Account account = new Account(repository, address);
-				byte[] unconfirmedLastReference = account.getUnconfirmedLastReference(null);
+				byte[] unconfirmedLastReference = account.getUnconfirmedLastReference();
 				if (unconfirmedLastReference != null)
 					accountData.setReference(unconfirmedLastReference);
 			}
@@ -109,9 +109,12 @@ public class AddressesResource {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_ADDRESS);
 
 		byte[] lastReference = null;
+
 		try (final Repository repository = RepositoryManager.getRepository()) {
 			Account account = new Account(repository, address);
 			lastReference = account.getUnconfirmedLastReference();
+			if (lastReference == null)
+				lastReference = account.getLastReference();
 		} catch (ApiException e) {
 			throw e;
 		} catch (DataException e) {
diff --git a/src/main/java/org/qora/repository/hsqldb/HSQLDBRepository.java b/src/main/java/org/qora/repository/hsqldb/HSQLDBRepository.java
index fc61cc21..59aa0aa9 100644
--- a/src/main/java/org/qora/repository/hsqldb/HSQLDBRepository.java
+++ b/src/main/java/org/qora/repository/hsqldb/HSQLDBRepository.java
@@ -11,8 +11,10 @@ import java.time.Instant;
 import java.time.OffsetDateTime;
 import java.time.ZoneOffset;
 import java.util.ArrayDeque;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Deque;
+import java.util.List;
 import java.util.TimeZone;
 
 import org.apache.logging.log4j.LogManager;
@@ -29,12 +31,10 @@ import org.qora.repository.Repository;
 import org.qora.repository.TransactionRepository;
 import org.qora.repository.VotingRepository;
 import org.qora.repository.hsqldb.transaction.HSQLDBTransactionRepository;
+import org.qora.settings.Settings;
 
 public class HSQLDBRepository implements Repository {
 
-	/** Queries that take longer than this (milliseconds) are logged */
-	private static final long MAX_QUERY_TIME = 1000L;
-
 	private static final Logger LOGGER = LogManager.getLogger(HSQLDBRepository.class);
 
 	public static final TimeZone UTC = TimeZone.getTimeZone("UTC");
@@ -42,11 +42,17 @@ public class HSQLDBRepository implements Repository {
 	protected Connection connection;
 	protected Deque<Savepoint> savepoints;
 	protected boolean debugState = false;
+	protected Long slowQueryThreshold = null;
+	protected List<String> queries;
 
 	// NB: no visibility modifier so only callable from within same package
 	HSQLDBRepository(Connection connection) {
 		this.connection = connection;
 		this.savepoints = new ArrayDeque<>(3);
+
+		this.slowQueryThreshold = Settings.getInstance().getSlowQueryThreshold();
+		if (this.slowQueryThreshold != null)
+			this.queries = new ArrayList<String>();
 	}
 
 	@Override
@@ -102,6 +108,9 @@ public class HSQLDBRepository implements Repository {
 			throw new DataException("commit error", e);
 		} finally {
 			this.savepoints.clear();
+
+			if (this.queries != null)
+				this.queries.clear();
 		}
 	}
 
@@ -113,6 +122,9 @@ public class HSQLDBRepository implements Repository {
 			throw new DataException("rollback error", e);
 		} finally {
 			this.savepoints.clear();
+
+			if (this.queries != null)
+				this.queries.clear();
 		}
 	}
 
@@ -121,6 +133,9 @@ public class HSQLDBRepository implements Repository {
 		try {
 			Savepoint savepoint = this.connection.setSavepoint();
 			this.savepoints.push(savepoint);
+
+			if (this.queries != null)
+				this.queries.add("SAVEPOINT");
 		} catch (SQLException e) {
 			throw new DataException("savepoint error", e);
 		}
@@ -135,6 +150,9 @@ public class HSQLDBRepository implements Repository {
 
 		try {
 			this.connection.rollback(savepoint);
+
+			if (this.queries != null)
+				this.queries.add("ROLLBACK TO SAVEPOINT");
 		} catch (SQLException e) {
 			throw new DataException("savepoint rollback error", e);
 		}
@@ -206,9 +224,17 @@ public class HSQLDBRepository implements Repository {
 		ResultSet resultSet = this.checkedExecuteResultSet(preparedStatement, objects);
 
 		long queryTime = System.currentTimeMillis() - beforeQuery;
-		if (queryTime > MAX_QUERY_TIME)
+		if (this.slowQueryThreshold != null && queryTime > this.slowQueryThreshold) {
 			LOGGER.info(String.format("HSQLDB query took %d ms: %s", queryTime, sql));
 
+			if (this.queries != null)
+				for (String query : this.queries)
+					LOGGER.info(query);
+		}
+
+		if (this.queries != null)
+			this.queries.add(sql);
+
 		return resultSet;
 	}
 
@@ -316,8 +342,13 @@ public class HSQLDBRepository implements Repository {
 	 * @throws SQLException
 	 */
 	public boolean exists(String tableName, String whereClause, Object... objects) throws SQLException {
-		try (PreparedStatement preparedStatement = this.connection.prepareStatement("SELECT TRUE FROM " + tableName + " WHERE " + whereClause + " LIMIT 1");
+		String sql = "SELECT TRUE FROM " + tableName + " WHERE " + whereClause + " LIMIT 1";
+
+		try (PreparedStatement preparedStatement = this.connection.prepareStatement(sql);
 				ResultSet resultSet = this.checkedExecuteResultSet(preparedStatement, objects)) {
+			if (this.queries != null)
+				this.queries.add(sql);
+
 			if (resultSet == null)
 				return false;
 
@@ -334,7 +365,12 @@ public class HSQLDBRepository implements Repository {
 	 * @throws SQLException
 	 */
 	public int delete(String tableName, String whereClause, Object... objects) throws SQLException {
-		try (PreparedStatement preparedStatement = this.connection.prepareStatement("DELETE FROM " + tableName + " WHERE " + whereClause)) {
+		String sql = "DELETE FROM " + tableName + " WHERE " + whereClause;
+
+		try (PreparedStatement preparedStatement = this.connection.prepareStatement(sql)) {
+			if (this.queries != null)
+				this.queries.add(sql);
+
 			return this.checkedExecuteUpdateCount(preparedStatement, objects);
 		}
 	}
@@ -346,7 +382,12 @@ public class HSQLDBRepository implements Repository {
 	 * @throws SQLException
 	 */
 	public int delete(String tableName) throws SQLException {
-		try (PreparedStatement preparedStatement = this.connection.prepareStatement("DELETE FROM " + tableName)) {
+		String sql = "DELETE FROM " + tableName;
+
+		try (PreparedStatement preparedStatement = this.connection.prepareStatement(sql)) {
+			if (this.queries != null)
+				this.queries.add(sql);
+
 			return this.checkedExecuteUpdateCount(preparedStatement);
 		}
 	}
@@ -376,6 +417,10 @@ public class HSQLDBRepository implements Repository {
 	public SQLException examineException(SQLException e) throws SQLException {
 		LOGGER.error("SQL error: " + e.getMessage());
 
+		if (this.queries != null)
+			for (String query : this.queries)
+				LOGGER.info(query);
+
 		// Serialization failure / potential deadlock - so list other sessions
 		try (ResultSet resultSet = this.checkedExecute(
 				"SELECT session_id, transaction, transaction_size, waiting_for_this, this_waiting_for, current_statement FROM Information_schema.system_sessions")) {
diff --git a/src/main/java/org/qora/settings/Settings.java b/src/main/java/org/qora/settings/Settings.java
index b8012fdc..6f525ce1 100644
--- a/src/main/java/org/qora/settings/Settings.java
+++ b/src/main/java/org/qora/settings/Settings.java
@@ -62,6 +62,12 @@ public class Settings {
 	private String blockchainConfig = "blockchain.json";
 	private boolean useBitcoinTestNet = false;
 
+	// Repository related
+	/** Queries that take longer than this are logged. (milliseconds) */
+	private Long slowQueryThreshold = null;
+	/** Repository storage path. */
+	private String repositoryPath = null;
+
 	// Constructors
 
 	private Settings() {
@@ -228,4 +234,12 @@ public class Settings {
 		return this.useBitcoinTestNet;
 	}
 
+	public Long getSlowQueryThreshold() {
+		return this.slowQueryThreshold;
+	}
+
+	public String getRepositoryPath() {
+		return this.repositoryPath;
+	}
+
 }
diff --git a/src/main/java/org/qora/transaction/Transaction.java b/src/main/java/org/qora/transaction/Transaction.java
index ad0182b7..2731f8b7 100644
--- a/src/main/java/org/qora/transaction/Transaction.java
+++ b/src/main/java/org/qora/transaction/Transaction.java
@@ -515,7 +515,10 @@ public abstract class Transaction {
 			if (!this.isValidTxGroupId())
 				return ValidationResult.INVALID_TX_GROUP_ID;
 
-			creator.setLastReference(creator.getUnconfirmedLastReference());
+			byte[] unconfirmedLastReference = creator.getUnconfirmedLastReference();
+			if (unconfirmedLastReference != null)
+				creator.setLastReference(unconfirmedLastReference);
+
 			ValidationResult result = this.isValid();
 
 			// Reject if unconfirmed pile already has X transactions from same creator