old_contents: /*  TTL cache:
   *
   */
  var cache = {
    memory: {}
  }
  
  /*  Save to cache:
   *
   *  @param  identifier  {string}
   *  @param  data        {string}
   *  @param  callback    {function}
   */
  cache.write = function (identifier, data, ttl, callback) {
    this.memory[identifier] = data;
    
    if (ttl) setTimeout(function () {
      delete this.memory[identifier]
    }.bind(this), ttl);
    
    if (callback) callback()
  }
  
  /*  Read from cache:
   *
   *  @param  identifier  {string}
   *  @param  callback    {function}
   */
  cache.read = function (identifier, callback) {
    return this.memory[identifier];
    
    if (callback) callback()
  }
  
  /*  Delete from cache:
   *
   *  @param  identifier  {string}
   *  @param  callback    {function}
   */
  cache.delete = function (identifier, callback) {
    delete this.memory[identifier]
    
    if (callback) callback()
  }
  
  /*  Destroy cache:
   *
   *  @param  callback  {function}
   */
  cache.destroy = function (callback) {
    this.memory = {};
    
    if (callback) callback(null, {
      error: false,
      success: true,
      message: 'Cache now empty'
    })
  }
  
  module.exports = cache
new_contents: /*  TTL cache:
   *
   */
  var cache = {
    memory: {}
  }
  
  /*  Save to cache:
   *
   *  @param  identifier  {string}
   *  @param  data        {string}
   *  @param  callback    {function}
   */
  cache.write = function (identifier, data, ttl, callback) {
    this.memory[identifier] = data;
    
    if (ttl) setTimeout(function () {
      delete this.memory[identifier]
    }.bind(this), ttl);
    
    if (callback) callback()
  }
  
  /*  Read from cache:
   *
   *  @param  identifier  {string}
   *  @param  callback    {function}
   */
  cache.read = function (identifier, callback) {
    if (callback) callback(this.memory[identifier]);
    else return this.memory[identifier];
  }
  
  /*  Delete from cache:
   *
   *  @param  identifier  {string}
   *  @param  callback    {function}
   */
  cache.delete = function (identifier, callback) {
    delete this.memory[identifier]
    
    if (callback) callback()
  }
  
  /*  Destroy cache:
   *
   *  @param  callback  {function}
   */
  cache.destroy = function (callback) {
    this.memory = {};
    
    if (callback) callback(null, {
      error: false,
      success: true,
      message: 'Cache now empty'
    })
  }
  
  module.exports = cache
subject: Read cache callback