diff --git a/lib/bcoin/chain.js b/lib/bcoin/chain.js
index 6f27c3f5..c156ad25 100644
--- a/lib/bcoin/chain.js
+++ b/lib/bcoin/chain.js
@@ -1126,10 +1126,10 @@ Chain.prototype.reset = function reset(height, callback, force) {
  * @param {Function} callback
  */
 
-Chain.prototype.resetTime = function resetTime(ts, callback, force) {
+Chain.prototype.resetTime = function resetTime(ts, callback) {
   var self = this;
 
-  callback = this._lock(resetTime, [ts, callback], force);
+  callback = this._lock(resetTime, [ts, callback]);
 
   if (!callback)
     return;
@@ -1172,13 +1172,13 @@ Chain.prototype.isBusy = function isBusy() {
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Chain.prototype.add = function add(block, callback, force) {
+Chain.prototype.add = function add(block, callback) {
   var self = this;
   var ret = {};
 
   assert(this.loaded);
 
-  callback = this._lock(add, [block, callback], force);
+  callback = this._lock(add, [block, callback]);
 
   if (!callback)
     return;
@@ -1708,13 +1708,13 @@ Chain.prototype.getProgress = function getProgress() {
  * @param {Function} callback - Returns [Error, {@link Hash}[]].
  */
 
-Chain.prototype.getLocator = function getLocator(start, callback, force) {
+Chain.prototype.getLocator = function getLocator(start, callback) {
   var self = this;
   var hashes = [];
   var step = 1;
   var height;
 
-  callback = this._lock(getLocator, [start, callback], force);
+  callback = this._lock(getLocator, [start, callback]);
 
   if (!callback)
     return;
diff --git a/lib/bcoin/locker.js b/lib/bcoin/locker.js
index 3605d18d..bde2eff1 100644
--- a/lib/bcoin/locker.js
+++ b/lib/bcoin/locker.js
@@ -138,8 +138,10 @@ Locker.prototype.lock = function lock(func, args, force) {
  */
 
 Locker.prototype.destroy = function destroy() {
-  this.pending.length = 0;
-  this.pendingMap = {};
+  if (this.add) {
+    this.pending.length = 0;
+    this.pendingMap = {};
+  }
   this.jobs.length = 0;
 };
 
@@ -149,6 +151,8 @@ Locker.prototype.destroy = function destroy() {
  */
 
 Locker.prototype.onDrain = function onDrain(callback) {
+  assert(this.add, 'Cannot wait for drain without add method.');
+
   if (this.pending.length === 0)
     return callback();
 
diff --git a/lib/bcoin/mempool.js b/lib/bcoin/mempool.js
index 43dc8ad4..75805fd6 100644
--- a/lib/bcoin/mempool.js
+++ b/lib/bcoin/mempool.js
@@ -163,6 +163,11 @@ Mempool.prototype.addBlock = function addBlock(block, callback) {
   var entries = [];
   var i, entry, tx, hash;
 
+  callback = this._lock(addBlock, [block, callback]);
+
+  if (!callback)
+    return;
+
   for (i = block.txs.length - 1; i >= 0; i--) {
     tx = block.txs[i];
     hash = tx.hash('hex');
@@ -189,7 +194,7 @@ Mempool.prototype.addBlock = function addBlock(block, callback) {
   if (this.fees)
     this.fees.processBlock(block.height, entries, this.chain.isFull());
 
-  callback();
+  utils.nextTick(callback);
 };
 
 /**
@@ -199,11 +204,11 @@ Mempool.prototype.addBlock = function addBlock(block, callback) {
  * @param {Function} callback
  */
 
-Mempool.prototype.removeBlock = function removeBlock(block, callback, force) {
+Mempool.prototype.removeBlock = function removeBlock(block, callback) {
   var self = this;
   var entry;
 
-  callback = this._lock(removeBlock, [block, callback], force);
+  callback = this._lock(removeBlock, [block, callback]);
 
   if (!callback)
     return;
@@ -512,14 +517,14 @@ Mempool.prototype.has = function has(hash) {
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Mempool.prototype.addTX = function addTX(tx, callback, force) {
+Mempool.prototype.addTX = function addTX(tx, callback) {
   var self = this;
   var lockFlags = constants.flags.STANDARD_LOCKTIME_FLAGS;
   var hash = tx.hash('hex');
   var ret = {};
   var entry;
 
-  callback = this._lock(addTX, [tx, callback], force);
+  callback = this._lock(addTX, [tx, callback]);
 
   if (!callback)
     return;
diff --git a/lib/bcoin/txdb.js b/lib/bcoin/txdb.js
index cadd487b..4397381c 100644
--- a/lib/bcoin/txdb.js
+++ b/lib/bcoin/txdb.js
@@ -1253,7 +1253,7 @@ TXDB.prototype.unconfirm = function unconfirm(hash, callback, force) {
  * @param {Function} callback
  */
 
-TXDB.prototype._unconfirm = function unconfirm(tx, info, callback, force) {
+TXDB.prototype._unconfirm = function unconfirm(tx, info, callback) {
   var self = this;
   var hash = tx.hash('hex');
   var i, account;
@@ -2265,17 +2265,16 @@ TXDB.prototype.getAccountBalance = function getBalance(account, callback) {
  * @param {Function} callback
  */
 
-TXDB.prototype.zap = function zap(account, age, callback, force) {
+TXDB.prototype.zap = function zap(account, age, callback) {
   var self = this;
 
   if (typeof age === 'function') {
-    force = callback;
     callback = age;
     age = account;
     account = null;
   }
 
-  callback = this._lock(zap, [account, age, callback], force);
+  callback = this._lock(zap, [account, age, callback]);
 
   if (!callback)
     return;
@@ -2304,7 +2303,7 @@ TXDB.prototype.zap = function zap(account, age, callback, force) {
  * @param {Function} callback
  */
 
-TXDB.prototype.abandon = function abandon(hash, callback, force) {
+TXDB.prototype.abandon = function abandon(hash, callback) {
   var self = this;
   this.has(layout.p(hash), function(err, result) {
     if (err)
@@ -2313,7 +2312,7 @@ TXDB.prototype.abandon = function abandon(hash, callback, force) {
     if (!result)
       return callback(new Error('TX not eligible.'));
 
-    self.remove(hash, callback, force);
+    self.remove(hash, callback);
   });
 };
 
diff --git a/lib/bcoin/wallet.js b/lib/bcoin/wallet.js
index 28d7c165..d5aded79 100644
--- a/lib/bcoin/wallet.js
+++ b/lib/bcoin/wallet.js
@@ -75,6 +75,24 @@ function Wallet(db, options) {
 
 utils.inherits(Wallet, EventEmitter);
 
+/**
+ * Invoke write mutex lock.
+ * @private
+ */
+
+Wallet.prototype._lockWrite = function _lockWrite(func, args, force) {
+  return this.writeLock.lock(func, args, force);
+};
+
+/**
+ * Invoke funding mutex lock.
+ * @private
+ */
+
+Wallet.prototype._lockFund = function _lockFund(func, args, force) {
+  return this.fundLock.lock(func, args, force);
+};
+
 /**
  * Inject properties from options object.
  * @private
@@ -245,7 +263,7 @@ Wallet.prototype.addKey = function addKey(account, key, callback) {
     account = 0;
   }
 
-  callback = this.writeLock.lock(addKey, [account, key, callback]);
+  callback = this._lockWrite(addKey, [account, key, callback]);
 
   if (!callback)
     return;
@@ -289,7 +307,7 @@ Wallet.prototype.removeKey = function removeKey(account, key, callback) {
     account = 0;
   }
 
-  callback = this.writeLock.lock(removeKey, [account, key, callback]);
+  callback = this._lockWrite(removeKey, [account, key, callback]);
 
   if (!callback)
     return;
@@ -333,7 +351,7 @@ Wallet.prototype.setPassphrase = function setPassphrase(old, new_, callback) {
     old = null;
   }
 
-  callback = this.writeLock.lock(setPassphrase, [old, new_, callback]);
+  callback = this._lockWrite(setPassphrase, [old, new_, callback]);
 
   if (!callback)
     return;
@@ -367,7 +385,7 @@ Wallet.prototype.retoken = function retoken(passphrase, callback) {
     passphrase = null;
   }
 
-  callback = this.writeLock.lock(retoken, [passphrase, callback]);
+  callback = this._lockWrite(retoken, [passphrase, callback]);
 
   if (!callback)
     return;
@@ -468,16 +486,18 @@ Wallet.prototype.getToken = function getToken(master, nonce) {
  * @param {Function} callback - Returns [Error, {@link Account}].
  */
 
-Wallet.prototype.createAccount = function createAccount(options, callback, force) {
+Wallet.prototype.createAccount = function createAccount(options, callback) {
   var self = this;
+  var passphrase = options.passphrase;
+  var timeout = options.timeout;
   var key;
 
-  callback = this.writeLock.lock(createAccount, [options, callback], force);
+  callback = this._lockWrite(createAccount, [options, callback]);
 
   if (!callback)
     return;
 
-  this.unlock(options.passphrase, options.timeout, function(err, master) {
+  this.unlock(passphrase, timeout, function(err, master) {
     if (err)
       return callback(err);
 
@@ -640,7 +660,7 @@ Wallet.prototype.createAddress = function createAddress(account, change, callbac
     account = 0;
   }
 
-  callback = this.writeLock.lock(createAddress, [account, change, callback]);
+  callback = this._lockWrite(createAddress, [account, change, callback]);
 
   if (!callback)
     return;
@@ -810,7 +830,7 @@ Wallet.prototype.fund = function fund(tx, options, callback, force) {
 
   // We use a lock here to ensure we
   // don't end up double spending coins.
-  callback = this.fundLock.lock(fund, [tx, options, callback], force);
+  callback = this._lockFund(fund, [tx, options, callback], force);
 
   if (!callback)
     return;
@@ -947,7 +967,7 @@ Wallet.prototype.createTX = function createTX(options, callback, force) {
 Wallet.prototype.send = function send(options, callback) {
   var self = this;
 
-  callback = this.fundLock.lock(send, [options, callback]);
+  callback = this._lockFund(send, [options, callback]);
 
   if (!callback)
     return;
@@ -1177,7 +1197,7 @@ Wallet.prototype.syncOutputDepth = function syncOutputDepth(info, callback) {
   var accounts = {};
   var i, path;
 
-  callback = this.writeLock.lock(syncOutputDepth, [info, callback]);
+  callback = this._lockWrite(syncOutputDepth, [info, callback]);
 
   if (!callback)
     return;
diff --git a/lib/bcoin/walletdb.js b/lib/bcoin/walletdb.js
index a5088af5..7d9a9e14 100644
--- a/lib/bcoin/walletdb.js
+++ b/lib/bcoin/walletdb.js
@@ -216,6 +216,33 @@ WalletDB.prototype._init = function _init() {
   }
 };
 
+/**
+ * Invoke wallet read mutex lock.
+ * @private
+ */
+
+WalletDB.prototype._lockRead = function _lockRead(key, func, args, force) {
+  return this.readLock.lock(key, func, args, force);
+};
+
+/**
+ * Invoke wallet write mutex lock.
+ * @private
+ */
+
+WalletDB.prototype._lockWrite = function _lockWrite(key, func, args, force) {
+  return this.writeLock.lock(key, func, args, force);
+};
+
+/**
+ * Invoke tx handling mutex lock.
+ * @private
+ */
+
+WalletDB.prototype._lockTX = function _lockTX(func, args, force) {
+  return this.txLock.lock(func, args, force);
+};
+
 /**
  * Open the walletdb, wait for the database to load.
  * @alias WalletDB#open
@@ -539,7 +566,7 @@ WalletDB.prototype._get = function get(wid, callback) {
   var self = this;
   var wallet;
 
-  callback = this.readLock.lock(wid, get, [wid, callback]);
+  callback = this._lockRead(wid, get, [wid, callback]);
 
   if (!callback)
     return;
@@ -613,7 +640,7 @@ WalletDB.prototype.create = function create(options, callback) {
     options = {};
   }
 
-  callback = this.writeLock.lock(options.id, create, [options, callback]);
+  callback = this._lockWrite(options.id, create, [options, callback]);
 
   if (!callback)
     return;
@@ -1337,11 +1364,11 @@ WalletDB.prototype.getWalletsByTX = function getWalletsByTX(hash, callback) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.addBlock = function addBlock(entry, txs, callback, force) {
+WalletDB.prototype.addBlock = function addBlock(entry, txs, callback) {
   var self = this;
   var block, matches, hash;
 
-  callback = this.txLock.lock(addBlock, [entry, txs, callback], force);
+  callback = this._lockTX(addBlock, [entry, txs, callback]);
 
   if (!callback)
     return;
@@ -1391,10 +1418,10 @@ WalletDB.prototype.addBlock = function addBlock(entry, txs, callback, force) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.removeBlock = function removeBlock(entry, callback, force) {
+WalletDB.prototype.removeBlock = function removeBlock(entry, callback) {
   var self = this;
 
-  callback = this.txLock.lock(removeBlock, [entry, callback], force);
+  callback = this._lockTX(removeBlock, [entry, callback]);
 
   if (!callback)
     return;
@@ -1464,6 +1491,11 @@ WalletDB.prototype.removeBlock = function removeBlock(entry, callback, force) {
 WalletDB.prototype.addTX = function addTX(tx, callback, force) {
   var self = this;
 
+  callback = this._lockTX(addTX, [tx, callback], force);
+
+  if (!callback)
+    return;
+
   assert(!tx.mutable, 'Cannot add mutable TX to wallet.');
 
   // Note: