diff --git a/lib/bcoin/mempool.js b/lib/bcoin/mempool.js
index 9214f2ab..3e7fbb7f 100644
--- a/lib/bcoin/mempool.js
+++ b/lib/bcoin/mempool.js
@@ -366,7 +366,7 @@ Mempool.prototype.limitMempoolSize = function limitMempoolSize(callback) {
   if (this.getSize() <= this.maxSize)
     return callback(null, true);
 
-  this.tx.getRange({
+  this.getRange({
     start: 0,
     end: utils.now() - constants.mempool.MEMPOOL_EXPIRY
   }, function(err, txs) {
@@ -405,13 +405,23 @@ Mempool.prototype.limitMempoolSize = function limitMempoolSize(callback) {
  * @param {Function} callback
  */
 
-Mempool.prototype.pruneOrphans = function pruneOrphans(callback) {
+Mempool.prototype.limitOrphans = function limitOrphans(callback) {
   var self = this;
-  utils.forEachSerial(Object.keys(this.orphans), function(hash, next) {
+  var orphans = Object.keys(this.orphans);
+  var i, hash;
+
+  (function next() {
     if (self.totalOrphans <= constants.mempool.MAX_ORPHAN_TX)
       return callback();
+
+    i = Math.random() * orphans.length | 0;
+    hash = orphans[i];
+    orphans.splice(i, 1);
+
+    bcoin.debug('Removing orphan %s from mempool.', utils.revHex(hash));
+
     self.removeOrphan(hash, next);
-  }, callback);
+  })();
 };
 
 /**
@@ -422,8 +432,6 @@ Mempool.prototype.pruneOrphans = function pruneOrphans(callback) {
  */
 
 Mempool.prototype.getTX = function getTX(hash, callback) {
-  if (hash instanceof bcoin.tx)
-    hash = hash.hash('hex');
   return this.tx.getTX(hash, callback);
 };
 
@@ -506,6 +514,16 @@ Mempool.prototype.hasTX = function hasTX(hash, callback) {
   return this.tx.hasTX(hash, callback);
 };
 
+/**
+ * Find transactions within a range.
+ * @param {Object} range
+ * @param {Function} callback - Returns [Error, {@link TX}[]].
+ */
+
+Mempool.prototype.getRange = function getRange(options, callback) {
+  return this.tx.getRange(options, callback);
+};
+
 /**
  * Test the mempool to see if it contains a transaction or an orphan.
  * @param {Hash} hash
@@ -775,13 +793,10 @@ Mempool.prototype.getMinRate = function getMinRate() {
   if (now > this.lastFeeUpdate + 10) {
     halflife = constants.mempool.FEE_HALFLIFE;
 
-    if (this.size < this.maxSize / 4) {
-      halflife /= 4;
-      halflife |= 0;
-    } else if (this.size < this.maxSize / 2) {
-      halflife /= 2;
-      halflife |= 0;
-    }
+    if (this.size < this.maxSize / 4)
+      halflife >>>= 2;
+    else if (this.size < this.maxSize / 2)
+      halflife >>>= 1;
 
     this.minFeeRate /= Math.pow(2.0, (now - this.lastFeeUpdate) / halflife | 0);
     this.minFeeRate |= 0;
@@ -1020,8 +1035,10 @@ Mempool.prototype.storeOrphan = function storeOrphan(tx, callback, force) {
   this.orphans[hash] = tx.toExtended(true);
   this.totalOrphans++;
 
+  bcoin.debug('Added orphan %s to mempool.', tx.rhash);
+
   if (this.totalOrphans > constants.mempool.MAX_ORPHAN_TX)
-    return this.pruneOrphans(callback);
+    return this.limitOrphans(callback);
 
   return callback();
 };