diff --git a/lib/cartodb/backends/cluster.js b/lib/cartodb/backends/cluster.js
index f858b27a..113dde65 100644
--- a/lib/cartodb/backends/cluster.js
+++ b/lib/cartodb/backends/cluster.js
@@ -6,8 +6,6 @@ const debug = require('debug')('backend:cluster');
 const AggregationMapConfig = require('../models/aggregation/aggregation-mapconfig');
 
 module.exports = class ClusterBackend {
-    // TODO: reduce complexity
-    // jshint maxcomplexity: 10
     getClusterFeatures (mapConfigProvider, params, callback) {
         mapConfigProvider.getMapConfig((err, _mapConfig) => {
             if (err) {
@@ -43,54 +41,19 @@ module.exports = class ClusterBackend {
 
             let { aggregation } = params;
 
-            if (aggregation !== undefined) {
-                try {
-                    aggregation = JSON.parse(aggregation);
-                } catch (err) {
-                    const error = new Error(`Invalid aggregation input, should be a a valid JSON`);
-                    error.http_status = 400;
-                    error.type = 'layer';
-                    error.subtype = 'aggregation';
-                    error.layer = {
-                        index: layerIndex,
-                        type: layer.type
-                    };
+            try {
+                aggregation = parseAggregation(aggregation);
+                validateAggregation(aggregation);
+            } catch (error) {
+                error.http_status = 400;
+                error.type = 'layer';
+                error.subtype = 'aggregation';
+                error.layer = {
+                    index: layerIndex,
+                    type: layer.type
+                };
 
-                    return callback(error);
-                }
-
-                const { columns, expressions } = aggregation;
-
-                if (!hasColumns(columns)) {
-                    const error = new Error(
-                        `Invalid aggregation input, columns should be and array of column names`
-                    );
-                    error.http_status = 400;
-                    error.type = 'layer';
-                    error.subtype = 'aggregation';
-                    error.layer = {
-                        index: layerIndex,
-                        type: layer.type
-                    };
-
-                    return callback(error);
-                }
-
-                if (expressions !== undefined) {
-                    try {
-                        validateExpressions(expressions);
-                    } catch (error) {
-                        error.http_status = 400;
-                        error.type = 'layer';
-                        error.subtype = 'aggregation';
-                        error.layer = {
-                            index: layerIndex,
-                            type: layer.type
-                        };
-
-                        return callback(error);
-                    }
-                }
+                return callback(error);
             }
 
             const query = layer.options.sql_raw;
@@ -229,22 +192,49 @@ function hasAggregationLayer (mapConfig, layerIndex) {
     return mapConfig.isAggregationLayer(layerIndex);
 }
 
+function parseAggregation (aggregation) {
+    if (aggregation !== undefined) {
+        try {
+            aggregation = JSON.parse(aggregation);
+        } catch (err) {
+            throw new Error(`Invalid aggregation input, should be a a valid JSON`);
+        }
+
+    }
+
+    return aggregation;
+}
+
+function validateAggregation (aggregation) {
+    if (aggregation !== undefined) {
+        const { columns, expressions } = aggregation;
+
+        if (!hasColumns(columns)) {
+            throw new Error(`Invalid aggregation input, columns should be and array of column names`);
+        }
+
+        validateExpressions(expressions);
+    }
+}
+
 function hasColumns (columns) {
     return Array.isArray(columns) && columns.length;
 }
 
 function validateExpressions (expressions) {
-    if (!isValidExpression(expressions)) {
-        throw new Error(`Invalid aggregation input, expressions should be and object with valid functions`);
-    }
-
-    for (const { aggregate_function, aggregated_column } of Object.values(expressions)) {
-        if (typeof aggregated_column !== 'string') {
-            throw new Error(`Invalid aggregation input, aggregated column should be an string`);
+    if (expressions !== undefined) {
+        if (!isValidExpression(expressions)) {
+            throw new Error(`Invalid aggregation input, expressions should be and object with valid functions`);
         }
 
-        if (typeof aggregate_function !== 'string') {
-            throw new Error(`Invalid aggregation input, aggregate function should be an string`);
+        for (const { aggregate_function, aggregated_column } of Object.values(expressions)) {
+            if (typeof aggregated_column !== 'string') {
+                throw new Error(`Invalid aggregation input, aggregated column should be an string`);
+            }
+
+            if (typeof aggregate_function !== 'string') {
+                throw new Error(`Invalid aggregation input, aggregate function should be an string`);
+            }
         }
     }
 }