diff --git a/lib/bcoin/txdb.js b/lib/bcoin/txdb.js
index ef4c449e..247e2740 100644
--- a/lib/bcoin/txdb.js
+++ b/lib/bcoin/txdb.js
@@ -96,7 +96,7 @@ TXDB.prototype._lock = function _lock(func, args, force) {
  * @param {Function} callback
  */
 
-TXDB.prototype._loadFilter = function loadFilter(callback) {
+TXDB.prototype.loadFilter = function loadFilter(callback) {
   var self = this;
 
   if (!this.filter)
@@ -119,7 +119,7 @@ TXDB.prototype._loadFilter = function loadFilter(callback) {
  * @returns {Boolean}
  */
 
-TXDB.prototype._testFilter = function _testFilter(addresses) {
+TXDB.prototype.testFilter = function testFilter(addresses) {
   var i;
 
   if (!this.filter)
@@ -143,7 +143,7 @@ TXDB.prototype.getMap = function getMap(tx, callback) {
   var addresses = tx.getHashes('hex');
   var map;
 
-  if (!this._testFilter(addresses))
+  if (!this.testFilter(addresses))
     return callback();
 
   this.mapAddresses(addresses, function(err, table) {
@@ -281,6 +281,34 @@ TXDB.prototype._getOrphans = function _getOrphans(key, callback) {
   });
 };
 
+/**
+ * Write the genesis block as the best hash.
+ * @param {Function} callback
+ */
+
+TXDB.prototype.writeGenesis = function writeGenesis(callback) {
+  var self = this;
+  var unlock, hash;
+
+  unlock = this._lock(writeGenesis, [callback]);
+
+  if (!unlock)
+    return;
+
+  callback = utils.wrap(callback, unlock);
+
+  self.db.has('R', function(err, result) {
+    if (err)
+      return callback(err);
+
+    if (result)
+      return callback();
+
+    hash = new Buffer(self.network.genesis.hash, 'hex');
+    self.db.put('R', hash, callback);
+  });
+};
+
 /**
  * Add a block's transactions and write the new best hash.
  * @param {Block} block
diff --git a/lib/bcoin/wallet.js b/lib/bcoin/wallet.js
index 65e7d22c..1ca85241 100644
--- a/lib/bcoin/wallet.js
+++ b/lib/bcoin/wallet.js
@@ -50,7 +50,8 @@ function Wallet(db, options) {
 
   this.db = db;
   this.network = db.network;
-  this.locker = new bcoin.locker(this);
+  this.writeLock = new bcoin.locker(this);
+  this.fillLock = new bcoin.locker(this);
 
   this.id = null;
   this.master = null;
@@ -220,6 +221,7 @@ Wallet.prototype.destroy = function destroy(callback) {
  */
 
 Wallet.prototype.addKey = function addKey(account, key, callback) {
+  var self = this;
   var unlock;
 
   if (typeof key === 'function') {
@@ -228,7 +230,7 @@ Wallet.prototype.addKey = function addKey(account, key, callback) {
     account = 0;
   }
 
-  unlock = this.locker.lock(addKey, [account, key, callback]);
+  unlock = this.writeLock.lock(addKey, [account, key, callback]);
 
   if (!unlock)
     return;
@@ -242,7 +244,19 @@ Wallet.prototype.addKey = function addKey(account, key, callback) {
     if (!account)
       return callback(new Error('Account not found.'));
 
-    account.addKey(key, callback);
+    self.start();
+
+    account.addKey(key, function(err, result) {
+      if (err) {
+        self.drop();
+        return callback(err);
+      }
+      self.commit(function(err) {
+        if (err)
+          return callback(err);
+        return callback(null, result);
+      });
+    });
   }, true);
 };
 
@@ -254,6 +268,7 @@ Wallet.prototype.addKey = function addKey(account, key, callback) {
  */
 
 Wallet.prototype.removeKey = function removeKey(account, key, callback) {
+  var self = this;
   var unlock;
 
   if (typeof key === 'function') {
@@ -262,7 +277,7 @@ Wallet.prototype.removeKey = function removeKey(account, key, callback) {
     account = 0;
   }
 
-  unlock = this.locker.lock(removeKey, [account, key, callback]);
+  unlock = this.writeLock.lock(removeKey, [account, key, callback]);
 
   if (!unlock)
     return;
@@ -276,7 +291,19 @@ Wallet.prototype.removeKey = function removeKey(account, key, callback) {
     if (!account)
       return callback(new Error('Account not found.'));
 
-    account.removeKey(key, callback);
+    self.start();
+
+    account.removeKey(key, function(err, result) {
+      if (err) {
+        self.drop();
+        return callback(err);
+      }
+      self.commit(function(err) {
+        if (err)
+          return callback(err);
+        return callback(null, result);
+      });
+    });
   }, true);
 };
 
@@ -297,7 +324,7 @@ Wallet.prototype.setPassphrase = function setPassphrase(old, new_, callback) {
     old = null;
   }
 
-  unlock = this.locker.lock(setPassphrase, [old, new_, callback]);
+  unlock = this.writeLock.lock(setPassphrase, [old, new_, callback]);
 
   if (!unlock)
     return;
@@ -312,7 +339,9 @@ Wallet.prototype.setPassphrase = function setPassphrase(old, new_, callback) {
       if (err)
         return callback(err);
 
-      return self.save(callback);
+      self.start();
+      self.save();
+      self.commit(callback);
     });
   });
 };
@@ -332,7 +361,7 @@ Wallet.prototype.retoken = function retoken(passphrase, callback) {
     passphrase = null;
   }
 
-  unlock = this.locker.lock(retoken, [passphrase, callback]);
+  unlock = this.writeLock.lock(retoken, [passphrase, callback]);
 
   if (!unlock)
     return;
@@ -346,7 +375,9 @@ Wallet.prototype.retoken = function retoken(passphrase, callback) {
     self.tokenDepth++;
     self.token = self.getToken(master, self.tokenDepth);
 
-    self.save(function(err) {
+    self.start();
+    self.save();
+    self.commit(function(err) {
       if (err)
         return callback(err);
       return callback(null, self.token);
@@ -431,7 +462,7 @@ Wallet.prototype.createAccount = function createAccount(options, callback, force
   var self = this;
   var key, unlock;
 
-  unlock = this.locker.lock(createAccount, [options, callback], force);
+  unlock = this.writeLock.lock(createAccount, [options, callback], force);
 
   if (!unlock)
     return;
@@ -457,13 +488,17 @@ Wallet.prototype.createAccount = function createAccount(options, callback, force
       n: options.n
     };
 
+    self.start();
+
     self.db.createAccount(options, function(err, account) {
-      if (err)
+      if (err) {
+        self.drop();
         return callback(err);
+      }
 
       self.accountDepth++;
-
-      self.save(function(err) {
+      self.save();
+      self.commit(function(err) {
         if (err)
           return callback(err);
         return callback(null, account);
@@ -487,14 +522,7 @@ Wallet.prototype.getAccounts = function getAccounts(callback) {
  * @param {Function} callback - Returns [Error, {@link Account}].
  */
 
-Wallet.prototype.getAccount = function getAccount(account, callback, force) {
-  var unlock = this.locker.lock(getAccount, [account, callback], force);
-
-  if (!unlock)
-    return;
-
-  callback = utils.wrap(callback, unlock);
-
+Wallet.prototype.getAccount = function getAccount(account, callback) {
   if (this.account) {
     if (account === 0 || account === 'default')
       return callback(null, this.account);
@@ -547,7 +575,7 @@ Wallet.prototype.createAddress = function createAddress(account, change, callbac
     account = 0;
   }
 
-  unlock = this.locker.lock(createAddress, [account, change, callback]);
+  unlock = this.writeLock.lock(createAddress, [account, change, callback]);
 
   if (!unlock)
     return;
@@ -561,7 +589,19 @@ Wallet.prototype.createAddress = function createAddress(account, change, callbac
     if (!account)
       return callback(new Error('Account not found.'));
 
-    account.createAddress(change, callback);
+    self.start();
+
+    account.createAddress(change, function(err, result) {
+      if (err) {
+        self.drop();
+        return callback(err);
+      }
+      self.commit(function(err) {
+        if (err)
+          return callback(err);
+        return callback(null, result);
+      });
+    });
   }, true);
 };
 
@@ -571,8 +611,35 @@ Wallet.prototype.createAddress = function createAddress(account, change, callbac
  * @param {Function} callback
  */
 
-Wallet.prototype.save = function save(callback) {
-  return this.db.save(this, callback);
+Wallet.prototype.save = function save() {
+  return this.db.save(this);
+};
+
+/**
+ * Start batch.
+ * @private
+ */
+
+Wallet.prototype.start = function start() {
+  return this.db.start(this.id);
+};
+
+/**
+ * Drop batch.
+ * @private
+ */
+
+Wallet.prototype.drop = function drop() {
+  return this.db.drop(this.id);
+};
+
+/**
+ * Save batch.
+ * @param {Function} callback
+ */
+
+Wallet.prototype.commit = function commit(callback) {
+  return this.db.commit(this.id, callback);
 };
 
 /**
@@ -620,7 +687,7 @@ Wallet.prototype.getPath = function getPath(address, callback) {
 
 Wallet.prototype.fill = function fill(tx, options, callback) {
   var self = this;
-  var rate;
+  var unlock, rate;
 
   if (typeof options === 'function') {
     callback = options;
@@ -630,6 +697,15 @@ Wallet.prototype.fill = function fill(tx, options, callback) {
   if (!options)
     options = {};
 
+  // We use a lock here to ensure we
+  // don't end up double spending coins.
+  unlock = this.fillLock.lock(fill, [tx, options, callback]);
+
+  if (!unlock)
+    return;
+
+  callback = utils.wrap(callback, unlock);
+
   if (!this.initialized)
     return callback(new Error('Wallet is not initialized.'));
 
@@ -920,7 +996,7 @@ Wallet.prototype.syncOutputDepth = function syncOutputDepth(tx, callback) {
   var receive = [];
   var i, path, unlock;
 
-  unlock = this.locker.lock(syncOutputDepth, [tx, callback]);
+  unlock = this.writeLock.lock(syncOutputDepth, [tx, callback]);
 
   if (!unlock)
     return;
@@ -940,6 +1016,8 @@ Wallet.prototype.syncOutputDepth = function syncOutputDepth(tx, callback) {
       accounts[path.account].push(path);
     }
 
+    self.start();
+
     utils.forEachSerial(Object.keys(accounts), function(index, next) {
       var paths = accounts[index];
       var receiveDepth = -1;
@@ -979,12 +1057,18 @@ Wallet.prototype.syncOutputDepth = function syncOutputDepth(tx, callback) {
 
           next();
         });
-      }, true);
+      });
     }, function(err) {
-      if (err)
+      if (err) {
+        self.drop();
         return callback(err);
+      }
 
-      return callback(null, receive, change);
+      self.commit(function(err) {
+        if (err)
+          return callback(err);
+        return callback(null, receive, change);
+      });
     });
   });
 };
@@ -1049,7 +1133,7 @@ Wallet.prototype.scan = function scan(maxGap, scanner, callback) {
     maxGap = null;
   }
 
-  unlock = this.locker.lock(scan, [maxGap, scanner, callback]);
+  unlock = this.writeLock.lock(scan, [maxGap, scanner, callback]);
 
   if (!unlock)
     return;
@@ -1059,17 +1143,31 @@ Wallet.prototype.scan = function scan(maxGap, scanner, callback) {
   if (!this.initialized)
     return callback(new Error('Wallet is not initialized.'));
 
+  self.start();
+
+  function done(err, total) {
+    if (err) {
+      self.drop();
+      return callback(err);
+    }
+    self.commit(function(err) {
+      if (err)
+        return callback(err);
+      return callback(null, total);
+    });
+  }
+
   (function next() {
     self.getAccount(index++, function(err, account) {
       if (err)
-        return callback(err);
+        return done(err);
 
       if (!account)
-        return callback(null, total);
+        return done(null, total);
 
       account.scan(maxGap, scanner, function(err, result) {
         if (err)
-          return callback(err);
+          return done(err);
 
         total += result;
 
@@ -1829,7 +1927,8 @@ Account.prototype.init = function init(callback) {
   // Waiting for more keys.
   if (this.keys.length !== this.n) {
     assert(!this.initialized);
-    return this.save(callback);
+    this.save();
+    return callback();
   }
 
   assert(this.receiveDepth === 0);
@@ -1870,14 +1969,6 @@ Account.prototype.pushKey = function pushKey(key) {
 
   assert(key, 'Key required.');
 
-  if (Array.isArray(key)) {
-    for (i = 0; i < key.length; i++) {
-      if (this.pushKey(key[i]))
-        result = true;
-    }
-    return result;
-  }
-
   if (key.accountKey)
     key = key.accountKey;
 
@@ -1924,14 +2015,6 @@ Account.prototype.spliceKey = function spliceKey(key) {
   var index = -1;
   var i;
 
-  if (Array.isArray(key)) {
-    for (i = 0; i < key.length; i++) {
-      if (this.spliceKey(key[i]))
-        result = true;
-    }
-    return result;
-  }
-
   assert(key, 'Key required.');
 
   if (key.accountKey)
@@ -1976,12 +2059,11 @@ Account.prototype.spliceKey = function spliceKey(key) {
 
 Account.prototype.addKey = function addKey(key, callback) {
   var result = false;
-  var error;
 
   try {
     result = this.pushKey(key);
   } catch (e) {
-    error = e;
+    return callback(e);
   }
 
   // Try to initialize again.
@@ -1989,9 +2071,6 @@ Account.prototype.addKey = function addKey(key, callback) {
     if (err)
       return callback(err);
 
-    if (error)
-      return callback(error);
-
     return callback(null, result);
   });
 };
@@ -2005,23 +2084,16 @@ Account.prototype.addKey = function addKey(key, callback) {
 
 Account.prototype.removeKey = function removeKey(key, callback) {
   var result = false;
-  var error;
 
   try {
     result = this.spliceKey(key);
   } catch (e) {
-    error = e;
+    return callback(e);
   }
 
-  this.save(function(err) {
-    if (err)
-      return callback(err);
+  this.save();
 
-    if (error)
-      return callback(error);
-
-    return callback(null, result);
-  });
+  return callback(null, result);
 };
 
 /**
@@ -2076,11 +2148,9 @@ Account.prototype.createAddress = function createAddress(change, callback) {
     if (err)
       return callback(err);
 
-    self.save(function(err) {
-      if (err)
-        return callback(err);
-      return callback(null, address);
-    });
+    self.save();
+
+    return callback(null, address);
   });
 };
 
@@ -2149,8 +2219,8 @@ Account.prototype.deriveAddress = function deriveAddress(change, index) {
  * @param {Function} callback
  */
 
-Account.prototype.save = function save(callback) {
-  return this.db.saveAccount(this, callback);
+Account.prototype.save = function save() {
+  return this.db.saveAccount(this);
 };
 
 /**
@@ -2209,12 +2279,9 @@ Account.prototype.setDepth = function setDepth(receiveDepth, changeDepth, callba
     if (err)
       return callback(err);
 
-    self.save(function(err) {
-      if (err)
-        return callback(err);
+    self.save();
 
-      return callback(null, receive, change);
-    });
+    return callback(null, receive, change);
   });
 };
 
@@ -2284,6 +2351,7 @@ Account.prototype.scan = function scan(maxGap, scanner, callback) {
             if (maxGap === 0 && index === depth) {
               if (!change)
                 return chainCheck(true);
+              self.save();
               return callback(null, total);
             }
 
@@ -2305,11 +2373,7 @@ Account.prototype.scan = function scan(maxGap, scanner, callback) {
             self.changeDepth = Math.max(depth, self.changeDepth - gap);
             self.changeAddress = self.deriveChange(self.changeDepth - 1);
 
-            self.save(function(err) {
-              if (err)
-                return callback(err);
-              return callback(null, total);
-            });
+            return callback(null, total);
           });
         });
       });
diff --git a/lib/bcoin/walletdb.js b/lib/bcoin/walletdb.js
index 4998e52b..1231ebfd 100644
--- a/lib/bcoin/walletdb.js
+++ b/lib/bcoin/walletdb.js
@@ -50,13 +50,14 @@ function WalletDB(options) {
   this.network = bcoin.network.get(options.network);
   this.fees = options.fees;
   this.logger = options.logger || bcoin.defaultLogger;
+  this.batches = {};
 
   // We need one read lock for `get` and `create`.
   // It will hold locks specific to wallet ids.
   this.readLock = new ReadLock(this);
 
-  this.accountCache = new bcoin.lru(10000, 1);
   this.walletCache = new bcoin.lru(10000, 1);
+  this.accountCache = new bcoin.lru(10000, 1);
   this.pathCache = new bcoin.lru(100000, 1);
 
   this.db = bcoin.ldb({
@@ -139,7 +140,12 @@ WalletDB.prototype._open = function open(callback) {
       if (err)
         return callback(err);
 
-      self.tx._loadFilter(callback);
+      self.tx.writeGenesis(function(err) {
+        if (err)
+          return callback(err);
+
+        self.tx.loadFilter(callback);
+      });
     });
   });
 };
@@ -176,6 +182,58 @@ WalletDB.prototype._lock = function lock(id, func, args, force) {
   return this.readLock.lock(id, func, args, force);
 };
 
+/**
+ * Start batch.
+ * @private
+ * @param {WalletID} id
+ */
+
+WalletDB.prototype.start = function start(id) {
+  assert(utils.isAlpha(id), 'Bad ID for batch.');
+  assert(!this.batches[id], 'Batch already started.');
+  this.batches[id] = this.db.batch();
+};
+
+/**
+ * Drop batch.
+ * @private
+ * @param {WalletID} id
+ */
+
+WalletDB.prototype.drop = function drop(id) {
+  var batch = this.batch(id);
+  batch.clear();
+  delete this.batches[id];
+};
+
+/**
+ * Get batch.
+ * @private
+ * @param {WalletID} id
+ * @returns {Leveldown.Batch}
+ */
+
+WalletDB.prototype.batch = function batch(id) {
+  var batch;
+  assert(utils.isAlpha(id), 'Bad ID for batch.');
+  batch = this.batches[id];
+  assert(batch, 'Batch does not exist.');
+  return batch;
+};
+
+/**
+ * Save batch.
+ * @private
+ * @param {WalletID} id
+ * @param {Function} callback
+ */
+
+WalletDB.prototype.commit = function commit(id, callback) {
+  var batch = this.batch(id);
+  delete this.batches[id];
+  batch.write(callback);
+};
+
 /**
  * Emit balance events after a tx is saved.
  * @private
@@ -495,13 +553,10 @@ WalletDB.prototype._get = function get(id, callback) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.save = function save(wallet, callback) {
-  if (!utils.isAlpha(wallet.id))
-    return callback(new Error('Wallet IDs must be alphanumeric.'));
-
+WalletDB.prototype.save = function save(wallet) {
+  var batch = this.batch(wallet.id);
   this.walletCache.set(wallet.id, wallet);
-
-  this.db.put('w/' + wallet.id, wallet.toRaw(), callback);
+  batch.put('w/' + wallet.id, wallet.toRaw());
 };
 
 /**
@@ -770,25 +825,17 @@ WalletDB.prototype.getAccountIndex = function getAccountIndex(id, name, callback
  * @param {Function} callback
  */
 
-WalletDB.prototype.saveAccount = function saveAccount(account, callback) {
-  var index, key, batch;
+WalletDB.prototype.saveAccount = function saveAccount(account) {
+  var batch = this.batch(account.id);
+  var index = new Buffer(4);
+  var key = account.id + '/' + account.accountIndex;
 
-  if (!utils.isAlpha(account.name))
-    return callback(new Error('Account names must be alphanumeric.'));
-
-  batch = this.db.batch();
-
-  index = new Buffer(4);
   index.writeUInt32LE(account.accountIndex, 0, true);
 
-  key = account.id + '/' + account.accountIndex;
-
   batch.put('a/' + key, account.toRaw());
   batch.put('i/' + account.id + '/' + account.name, index);
 
   this.accountCache.set(key, account);
-
-  batch.write(callback);
 };
 
 /**
@@ -863,7 +910,7 @@ WalletDB.prototype.hasAccount = function hasAccount(id, account, callback) {
 WalletDB.prototype.saveAddress = function saveAddress(id, addresses, callback) {
   var self = this;
   var items = [];
-  var batch = this.db.batch();
+  var batch = this.batch(id);
   var i, address, path;
 
   if (!Array.isArray(addresses))
@@ -910,12 +957,7 @@ WalletDB.prototype.saveAddress = function saveAddress(id, addresses, callback) {
 
       next();
     });
-  }, function(err) {
-    if (err)
-      return callback(err);
-
-    batch.write(callback);
-  });
+  }, callback);
 };
 
 /**