diff --git a/lib/plugins.js b/lib/plugins.js
index 43883954..9cc982b3 100644
--- a/lib/plugins.js
+++ b/lib/plugins.js
@@ -1,61 +1,61 @@
 'use strict'
 
-var fs = require('fs')
-var R = require('ramda')
-var async = require('async')
-var HKDF = require('node-hkdf-sync')
-var BigNumber = require('bignumber.js')
+const fs = require('fs')
+const R = require('ramda')
+const async = require('async')
+const HKDF = require('node-hkdf-sync')
+const BigNumber = require('bignumber.js')
 BigNumber.config({CRYPTO: true})
-var db = require('./postgresql_interface')
-var logger = require('./logger')
-var notifier = require('./notifier')
+const db = require('./postgresql_interface')
+const logger = require('./logger')
+const notifier = require('./notifier')
 
-var uuid = require('node-uuid')
-var tradeIntervals = {}
+const uuid = require('node-uuid')
+const tradeIntervals = {}
 
-var CHECK_NOTIFICATION_INTERVAL = 60 * 1000
-var ALERT_SEND_INTERVAL = 60 * 60 * 1000
-var POLLING_RATE = 60 * 1000 // poll each minute
-var INCOMING_TX_INTERVAL = 5 * 1000
-var LIVE_INCOMING_TX_INTERVAL = 30 * 1000
-var STALE_INCOMING_TX_AGE = 7 * 24 * 60 * 60 * 1000
-var UNNOTIFIED_INTERVAL = 60 * 1000
-var MAX_NOTIFY_AGE = 48 * 60 * 60 * 1000
-var MIN_NOTIFY_AGE = 5 * 60 * 1000
-var TRANSACTION_EXPIRATION = 48 * 60 * 60 * 1000
-var SWEEP_LIVE_HD_INTERVAL = 60 * 1000
-var SWEEP_OLD_HD_INTERVAL = 2 * 60 * 1000
-var TRADE_INTERVAL = 60 * 1000
-var TRADE_TTL = 5 * 60 * 1000
+const CHECK_NOTIFICATION_INTERVAL = 60 * 1000
+const ALERT_SEND_INTERVAL = 60 * 60 * 1000
+const POLLING_RATE = 60 * 1000 // poll each minute
+const INCOMING_TX_INTERVAL = 5 * 1000
+const LIVE_INCOMING_TX_INTERVAL = 30 * 1000
+const STALE_INCOMING_TX_AGE = 7 * 24 * 60 * 60 * 1000
+const UNNOTIFIED_INTERVAL = 60 * 1000
+const MAX_NOTIFY_AGE = 48 * 60 * 60 * 1000
+const MIN_NOTIFY_AGE = 5 * 60 * 1000
+const TRANSACTION_EXPIRATION = 48 * 60 * 60 * 1000
+const SWEEP_LIVE_HD_INTERVAL = 60 * 1000
+const SWEEP_OLD_HD_INTERVAL = 2 * 60 * 1000
+const TRADE_INTERVAL = 60 * 1000
+const TRADE_TTL = 5 * 60 * 1000
 
-var cryptoCodes = null
+let cryptoCodes = null
 
-var tickerPlugins = {}
-var traderPlugins = {}
-var walletPlugins = {}
-var idVerifierPlugin = null
-var infoPlugin = null
-var emailPlugin = null
-var smsPlugin = null
-var hkdf = null
+const tickerPlugins = {}
+const traderPlugins = {}
+const walletPlugins = {}
+let idVerifierPlugin = null
+let infoPlugin = null
+let emailPlugin = null
+let smsPlugin = null
+let hkdf = null
 
-var currentlyUsedPlugins = {}
+const currentlyUsedPlugins = {}
 
-var cachedConfig = null
-var deviceCurrency = 'USD'
+let cachedConfig = null
+let deviceCurrency = 'USD'
 
-var lastBalances = {}
-var lastRates = {}
+const lastBalances = {}
+const lastRates = {}
 
-var tradesQueues = {}
+const tradesQueues = {}
 
-var coins = {
+const coins = {
   BTC: {unitScale: 8},
   ETH: {unitScale: 18}
 }
 
-var alertFingerprint = null
-var lastAlertTime = null
+let alertFingerprint = null
+let lastAlertTime = null
 
 exports.init = function init (connectionString) {
   const masterSeed = fs.readFileSync('seeds/seed.txt', 'utf8').trim()
@@ -66,7 +66,7 @@ exports.init = function init (connectionString) {
 
 function loadPlugin (name, config) {
   // plugins definitions
-  var moduleMethods = {
+  const moduleMethods = {
     ticker: ['ticker'],
     trader: ['purchase', 'sell'],
     wallet: ['balance', 'sendBitcoins', 'newAddress'],
@@ -75,7 +75,7 @@ function loadPlugin (name, config) {
     email: ['sendMessage']
   }
 
-  var plugin = null
+  let plugin = null
 
   // each used plugin MUST be installed
   try {
@@ -97,8 +97,8 @@ function loadPlugin (name, config) {
       '\'SUPPORTED_MODULES\' constant')
   }
 
-  plugin.SUPPORTED_MODULES.forEach(function (moduleName) {
-    moduleMethods[moduleName].forEach(function (methodName) {
+  plugin.SUPPORTED_MODULES.forEach(moduleName => {
+    moduleMethods[moduleName].forEach(methodName => {
       if (typeof plugin[methodName] !== 'function') {
         throw new Error('\'' + name + '\' declares \'' + moduleName +
           '\', but fails to implement \'' + methodName + '\' method')
@@ -115,7 +115,7 @@ function loadPlugin (name, config) {
   if (typeof plugin.config !== 'function') {
     logger.warn(new Error('\'' + name +
       '\' fails to implement *recommended* \'config\' method'))
-    plugin.config = function () {}
+    plugin.config = () => {}
   } else if (config !== null) {
     plugin.config(config, logger) // only when plugin supports it, and config is passed
   }
@@ -127,17 +127,17 @@ function loadOrConfigPlugin (pluginHandle, pluginType, cryptoCode, options,
     onChangeCallback) {
   cryptoCode = cryptoCode || 'BTC'
 
-  var currentName = cryptoCode === 'any' || cryptoCode === 'BTC'
+  const currentName = cryptoCode === 'any' || cryptoCode === 'BTC'
   ? cachedConfig.exchanges.plugins.current[pluginType]
   : cachedConfig.exchanges.plugins.current[cryptoCode][pluginType]
 
   currentlyUsedPlugins[cryptoCode] = currentlyUsedPlugins[cryptoCode] || {}
 
-  var pluginChanged = currentlyUsedPlugins[cryptoCode][pluginType] !== currentName
+  const pluginChanged = currentlyUsedPlugins[cryptoCode][pluginType] !== currentName
 
   if (!currentName) pluginHandle = null
   else { // some plugins may be disabled
-    var pluginConfig = cachedConfig.exchanges.plugins.settings[currentName] || {}
+    const pluginConfig = cachedConfig.exchanges.plugins.settings[currentName] || {}
 
     const mergedConfig = R.merge(pluginConfig, options)
 
@@ -167,7 +167,7 @@ exports.configure = function configure (config) {
   deviceCurrency = config.exchanges.settings.currency
   cryptoCodes = config.exchanges.settings.coins || ['BTC', 'ETH']
 
-  cryptoCodes.forEach(function (cryptoCode) {
+  cryptoCodes.forEach(cryptoCode => {
   // TICKER [required] configure (or load)
     loadOrConfigPlugin(
       tickerPlugins[cryptoCode],
@@ -252,15 +252,15 @@ function buildCartridges (cartridges, virtualCartridges, rec) {
         count: parseInt(rec.counts[1], 10)
       }
     ],
-    virtualCartridges: virtualCartridges,
+    virtualCartridges,
     id: rec.id
   }
 }
 
 exports.pollQueries = function pollQueries (session, cb) {
-  var cartridges = cachedConfig.exchanges.settings.cartridges
+  const cartridges = cachedConfig.exchanges.settings.cartridges
   if (!cartridges) return cb(null, {})
-  var virtualCartridges = cachedConfig.exchanges.settings.virtualCartridges
+  const virtualCartridges = cachedConfig.exchanges.settings.virtualCartridges
 
   return db.cartridgeCounts(session)
   .then(result => ({
@@ -278,8 +278,8 @@ function _sendCoins (toAddress, cryptoAtoms, cryptoCode) {
 }
 
 function _sendCoinsCb (toAddress, cryptoAtoms, cryptoCode, cb) {
-  var walletPlugin = walletPlugins[cryptoCode]
-  var transactionFee = cachedConfig.exchanges.settings.transactionFee
+  const walletPlugin = walletPlugins[cryptoCode]
+  const transactionFee = cachedConfig.exchanges.settings.transactionFee
   logger.debug('Sending coins [%s] to: %s', cryptoCode, toAddress)
 
   if (cryptoCode === 'BTC') {
@@ -300,7 +300,7 @@ function executeTx (session, tx) {
     .then(() => pollBalance(tx.cryptoCode))
     .then(() => ({
       statusCode: 201, // Created
-      txHash: txHash,
+      txHash,
       txId: tx.txId
     }))
   })
@@ -310,15 +310,15 @@ function executeTx (session, tx) {
 exports.trade = function trade (session, rawTrade) {
   // TODO: move this to DB, too
   // add bill to trader queue (if trader is enabled)
-  var cryptoCode = rawTrade.cryptoCode || 'BTC'
-  var traderPlugin = traderPlugins[cryptoCode]
+  const cryptoCode = rawTrade.cryptoCode || 'BTC'
+  const traderPlugin = traderPlugins[cryptoCode]
 
   if (traderPlugin) {
     logger.debug('[%s] Pushing trade: %d', cryptoCode, rawTrade.cryptoAtoms)
     tradesQueues[cryptoCode].push({
       currency: rawTrade.currency,
       cryptoAtoms: rawTrade.cryptoAtoms,
-      cryptoCode: cryptoCode,
+      cryptoCode,
       timestamp: Date.now()
     })
   }
@@ -327,7 +327,7 @@ exports.trade = function trade (session, rawTrade) {
 }
 
 exports.stateChange = function stateChange (session, rec, cb) {
-  var event = {
+  const event = {
     id: rec.uuid,
     fingerprint: session.fingerprint,
     eventType: 'stateChange',
@@ -338,7 +338,7 @@ exports.stateChange = function stateChange (session, rec, cb) {
 }
 
 exports.recordPing = function recordPing (session, rec, cb) {
-  var event = {
+  const event = {
     id: uuid.v4(),
     fingerprint: session.fingerprint,
     eventType: 'ping',
@@ -349,23 +349,23 @@ exports.recordPing = function recordPing (session, rec, cb) {
 }
 
 exports.sendCoins = function sendCoins (session, rawTx) {
-  var _session = {id: rawTx.sessionId || session.id, fingerprint: session.fingerprint}
+  const _session = {id: rawTx.sessionId || session.id, fingerprint: session.fingerprint}
   return executeTx(_session, rawTx)
 }
 
 exports.cashOut = function cashOut (session, tx) {
-  var cryptoCode = tx.cryptoCode || 'BTC'
-  var walletPlugin = walletPlugins[cryptoCode]
+  const cryptoCode = tx.cryptoCode || 'BTC'
+  const walletPlugin = walletPlugins[cryptoCode]
 
   return db.nextCashOutSerialHD(tx.sessionId, cryptoCode)
   .then(serialNumber => new Promise((resolve, reject) => {
     const tmpInfo = {
       label: 'TX ' + Date.now(),
       account: 'deposit',
-      serialNumber: serialNumber
+      serialNumber
     }
 
-    walletPlugin.newAddress(tmpInfo, function (err, address) {
+    walletPlugin.newAddress(tmpInfo, (err, address) => {
       if (err) return reject(err)
 
       const newTx = R.assoc('toAddress', address, tx)
@@ -380,25 +380,25 @@ exports.dispenseAck = function dispenseAck (session, rec) {
 }
 
 exports.fiatBalance = function fiatBalance (cryptoCode) {
-  var deviceRate = exports.getDeviceRate(cryptoCode)
+  const deviceRate = exports.getDeviceRate(cryptoCode)
   if (!deviceRate) return null
-  var rawRate = deviceRate.rates.ask
-  var commission = cachedConfig.exchanges.settings.commission
-  var lastBalanceRec = lastBalances[cryptoCode]
+  const rawRate = deviceRate.rates.ask
+  const commission = cachedConfig.exchanges.settings.commission
+  const lastBalanceRec = lastBalances[cryptoCode]
   if (!lastBalanceRec) return null
-  var lastBalance = lastBalanceRec.balance
+  const lastBalance = lastBalanceRec.balance
 
   if (!rawRate || !lastBalance) return null
 
   // The rate is actually our commission times real rate.
-  var rate = rawRate.times(commission)
+  const rate = rawRate.times(commission)
 
   // `lowBalanceMargin` is our safety net. It's a number > 1, and we divide
   // all our balances by it to provide a safety margin.
-  var lowBalanceMargin = cachedConfig.exchanges.settings.lowBalanceMargin
+  const lowBalanceMargin = cachedConfig.exchanges.settings.lowBalanceMargin
 
-  var unitScale = new BigNumber(10).pow(coins[cryptoCode].unitScale)
-  var fiatTransferBalance = lastBalance.div(unitScale).times(rate).div(lowBalanceMargin)
+  const unitScale = new BigNumber(10).pow(coins[cryptoCode].unitScale)
+  const fiatTransferBalance = lastBalance.div(unitScale).times(rate).div(lowBalanceMargin)
 
   return {timestamp: lastBalanceRec.timestamp, balance: fiatTransferBalance.round(3).toNumber()}
 }
@@ -411,6 +411,7 @@ function processTxStatus (tx) {
 
   return walletPlugin.getStatus(tx.toAddress, tx.cryptoAtoms)
   .then(res => db.updateTxStatus(tx, res.status))
+  .catch(err => logger.error('[%s] Tx status processing error: %s', cryptoCode, err.message))
 }
 
 function notifyConfirmation (tx) {
@@ -454,7 +455,7 @@ function monitorUnnotified () {
 exports.startPolling = function startPolling () {
   executeTrades()
 
-  cryptoCodes.forEach(function (cryptoCode) {
+  cryptoCodes.forEach(cryptoCode => {
     setInterval(async.apply(pollBalance, cryptoCode), POLLING_RATE)
     setInterval(async.apply(pollRate, cryptoCode), POLLING_RATE)
     startTrader(cryptoCode)
@@ -478,13 +479,13 @@ function startTrader (cryptoCode) {
   // since configuration can always change in `Trader#configure`.
   // `Trader#executeTrades` returns early if we don't have a trade exchange
   // configured at the moment.
-  var traderPlugin = traderPlugins[cryptoCode]
+  const traderPlugin = traderPlugins[cryptoCode]
   if (!traderPlugin || tradeIntervals[cryptoCode]) return
 
   logger.debug('[%s] startTrader', cryptoCode)
 
   tradeIntervals[cryptoCode] = setInterval(
-    function () { executeTrades(cryptoCode) },
+    () => { executeTrades(cryptoCode) },
     TRADE_INTERVAL
   )
 }
@@ -501,9 +502,9 @@ function stopTrader (cryptoCode) {
 function pollBalance (cryptoCode, cb) {
   logger.debug('[%s] collecting balance', cryptoCode)
 
-  var walletPlugin = walletPlugins[cryptoCode]
+  const walletPlugin = walletPlugins[cryptoCode]
 
-  walletPlugin.balance(function (err, balance) {
+  walletPlugin.balance((err, balance) => {
     if (err) {
       logger.error('[%s] Error loading balance: %s', cryptoCode, err.message)
       return cb && cb(err)
@@ -517,24 +518,24 @@ function pollBalance (cryptoCode, cb) {
 }
 
 function pollRate (cryptoCode, cb) {
-  var tickerPlugin = tickerPlugins[cryptoCode]
+  const tickerPlugin = tickerPlugins[cryptoCode]
   logger.debug('[%s] polling for rates (%s)', cryptoCode, tickerPlugin.NAME)
 
-  var currencies = deviceCurrency
+  let currencies = deviceCurrency
   if (typeof currencies === 'string') currencies = [currencies]
 
-  var tickerF = cryptoCode === 'BTC'
+  const tickerF = cryptoCode === 'BTC'
   ? async.apply(tickerPlugin.ticker, currencies)
   : async.apply(tickerPlugin.ticker, currencies, cryptoCode)
 
-  tickerF(function (err, resRates) {
+  tickerF((err, resRates) => {
     if (err) {
       logger.error(err)
       return cb && cb(err)
     }
 
     resRates.timestamp = Date.now()
-    var rates = resRates[deviceCurrency].rates
+    const rates = resRates[deviceCurrency].rates
     if (rates) {
       rates.ask = rates.ask && new BigNumber(rates.ask)
       rates.bid = rates.bid && new BigNumber(rates.bid)
@@ -552,7 +553,7 @@ function pollRate (cryptoCode, cb) {
  */
 
 exports.getDeviceRate = function getDeviceRate (cryptoCode) {
-  var lastRate = lastRates[cryptoCode]
+  const lastRate = lastRates[cryptoCode]
   if (!lastRate) return null
 
   return lastRate[deviceCurrency]
@@ -562,14 +563,14 @@ exports.getDeviceRate = function getDeviceRate (cryptoCode) {
  * Trader functions
  */
 function purchase (trade, cb) {
-  var cryptoCode = trade.cryptoCode
-  var traderPlugin = traderPlugins[cryptoCode]
-  var opts = {
-    cryptoCode: cryptoCode,
+  const cryptoCode = trade.cryptoCode
+  const traderPlugin = traderPlugins[cryptoCode]
+  const opts = {
+    cryptoCode,
     fiat: deviceCurrency
   }
 
-  traderPlugin.purchase(trade.cryptoAtoms, opts, function (err) {
+  traderPlugin.purchase(trade.cryptoAtoms, opts, err => {
     if (err) return cb(err)
     pollBalance(cryptoCode)
     if (typeof cb === 'function') cb()
@@ -599,10 +600,10 @@ function consolidateTrades (cryptoCode) {
   const cryptoAtoms = filtered
   .reduce((prev, current) => prev.plus(current.cryptoAtoms), new BigNumber(0))
 
-  var consolidatedTrade = {
+  const consolidatedTrade = {
     currency: deviceCurrency,
-    cryptoAtoms: cryptoAtoms,
-    cryptoCode: cryptoCode
+    cryptoAtoms,
+    cryptoCode
   }
 
   tradesQueues[cryptoCode] = []
@@ -612,12 +613,12 @@ function consolidateTrades (cryptoCode) {
 }
 
 function executeTrades (cryptoCode) {
-  var traderPlugin = traderPlugins[cryptoCode]
+  const traderPlugin = traderPlugins[cryptoCode]
   if (!traderPlugin) return
 
   logger.debug('[%s] checking for trades', cryptoCode)
 
-  var trade = consolidateTrades(cryptoCode)
+  const trade = consolidateTrades(cryptoCode)
   if (trade === null) return logger.debug('[%s] no trades', cryptoCode)
 
   if (trade.cryptoAtoms.eq(0)) {
@@ -626,7 +627,7 @@ function executeTrades (cryptoCode) {
   }
 
   logger.debug('making a trade: %d', trade.cryptoAtoms.toString())
-  purchase(trade, function (err) {
+  purchase(trade, err => {
     if (err) {
       tradesQueues[cryptoCode].push(trade)
       if (err.name !== 'orderTooSmall') return logger.error(err)
@@ -652,8 +653,8 @@ exports.getcryptoCodes = function getcryptoCodes () {
 }
 
 function sendMessage (rec) {
-  var pluginTypes = JSON.parse(cachedConfig.exchanges.plugins.current.notify)
-  var pluginPromises = pluginTypes.map(function (pluginType) {
+  const pluginTypes = JSON.parse(cachedConfig.exchanges.plugins.current.notify)
+  const pluginPromises = pluginTypes.map(pluginType => {
     if (pluginType === 'email') return emailPlugin.sendMessage(rec)
     if (pluginType === 'sms') return smsPlugin.sendMessage(rec)
     throw new Error('No such plugin type: ' + pluginType)
@@ -663,13 +664,13 @@ function sendMessage (rec) {
 exports.sendMessage = sendMessage
 
 function sendNoAlerts () {
-  var subject = '[Lamassu] All clear'
-  var rec = {
+  const subject = '[Lamassu] All clear'
+  const rec = {
     sms: {
       body: subject
     },
     email: {
-      subject: subject,
+      subject,
       body: 'No errors are reported for your machines.'
     }
   }
@@ -678,26 +679,26 @@ function sendNoAlerts () {
 
 function checkNotification () {
   return notifier.checkStatus()
-  .then(function (alertRec) {
-    var fingerprint = notifier.alertFingerprint(alertRec)
+  .then(alertRec => {
+    const fingerprint = notifier.alertFingerprint(alertRec)
     if (!fingerprint) {
-      var inAlert = !!alertFingerprint
+      const inAlert = !!alertFingerprint
       alertFingerprint = null
       lastAlertTime = null
       if (inAlert) return sendNoAlerts()
     }
 
-    var alertChanged = fingerprint === alertFingerprint &&
+    const alertChanged = fingerprint === alertFingerprint &&
       lastAlertTime - Date.now() < ALERT_SEND_INTERVAL
     if (alertChanged) return
 
-    var subject = notifier.alertSubject(alertRec)
-    var rec = {
+    const subject = notifier.alertSubject(alertRec)
+    const rec = {
       sms: {
         body: subject
       },
       email: {
-        subject: subject,
+        subject,
         body: notifier.printEmailAlerts(alertRec)
       }
     }
@@ -706,22 +707,22 @@ function checkNotification () {
 
     return sendMessage(rec)
   })
-  .then(function () {
+  .then(() => {
     logger.debug('Successfully sent alerts')
   })
-  .catch(function (err) {
+  .catch(err => {
     logger.error(err)
   })
 }
 
 function checkBalances () {
-  var cryptoCodes = exports.getcryptoCodes()
+  const cryptoCodes = exports.getcryptoCodes()
 
-  var balances = []
-  cryptoCodes.forEach(function (cryptoCode) {
-    var balanceRec = exports.fiatBalance(cryptoCode)
+  const balances = []
+  cryptoCodes.forEach(cryptoCode => {
+    const balanceRec = exports.fiatBalance(cryptoCode)
     if (!balanceRec) return
-    var rec = {fiatBalance: balanceRec.balance, cryptoCode: cryptoCode,
+    const rec = {fiatBalance: balanceRec.balance, cryptoCode,
       fiatCode: deviceCurrency}
     balances.push(rec)
   })
@@ -730,7 +731,7 @@ function checkBalances () {
 }
 
 exports.startCheckingNotification = function startCheckingNotification () {
-  var config = cachedConfig.exchanges.plugins.settings.notifier
+  const config = cachedConfig.exchanges.plugins.settings.notifier
   notifier.init(db, checkBalances, config)
   checkNotification()
   setInterval(checkNotification, CHECK_NOTIFICATION_INTERVAL)
@@ -782,13 +783,9 @@ exports.requestDispense = function requestDispense (tx) {
   return db.addDispenseRequest(tx)
 }
 
-exports.cachedResponse = function (session, path, method) {
-  return db.cachedResponse(session, path, method)
-}
+exports.cachedResponse = (session, path, method) => db.cachedResponse(session, path, method)
 
-exports.cacheResponse = function (session, path, method, body) {
-  return db.cacheResponse(session, path, method, body)
-}
+exports.cacheResponse = (session, path, method, body) => db.cacheResponse(session, path, method, body)
 
 function sweepHD (row) {
   const cryptoCode = row.crypto_code
@@ -800,7 +797,7 @@ function sweepHD (row) {
       return db.markSwept(row.session_id)
     }
   })
-  .catch(err => logger.error(err))
+  .catch(err => logger.error('[%s] Sweep error: %s', cryptoCode, err.message))
 }
 
 function sweepLiveHD () {