diff --git a/x-pack/plugins/ml/public/application/components/entity_cell/entity_cell.js b/x-pack/plugins/ml/public/application/components/entity_cell/entity_cell.js
index 02a9e569f28a4..d3917412bfb7b 100644
--- a/x-pack/plugins/ml/public/application/components/entity_cell/entity_cell.js
+++ b/x-pack/plugins/ml/public/application/components/entity_cell/entity_cell.js
@@ -10,6 +10,8 @@ import React from 'react';
 import { EuiButtonIcon, EuiFlexGroup, EuiFlexItem, EuiText, EuiToolTip } from '@elastic/eui';
 import { FormattedMessage } from '@kbn/i18n/react';
 import { i18n } from '@kbn/i18n';
+import { EMPTY_FIELD_VALUE_LABEL } from '../../timeseriesexplorer/components/entity_control/entity_control';
+import { MLCATEGORY } from '../../../../common/constants/field_types';
 
 function getAddFilter({ entityName, entityValue, filter }) {
   return (
@@ -68,7 +70,11 @@ export const EntityCell = function EntityCell({
   filter,
   wrapText = false,
 }) {
-  const valueText = entityName !== 'mlcategory' ? entityValue : `mlcategory ${entityValue}`;
+  let valueText = entityValue === '' ? <i>{EMPTY_FIELD_VALUE_LABEL}</i> : entityValue;
+  if (entityName === MLCATEGORY) {
+    valueText = `${MLCATEGORY} ${valueText}`;
+  }
+
   const textStyle = { maxWidth: '100%' };
   const textWrapperClass = wrapText ? 'field-value-long' : 'field-value-short';
   const shouldDisplayIcons =
diff --git a/x-pack/plugins/ml/public/application/explorer/explorer_swimlane.js b/x-pack/plugins/ml/public/application/explorer/explorer_swimlane.js
index e8cb8377a656d..d7333f00c89cd 100644
--- a/x-pack/plugins/ml/public/application/explorer/explorer_swimlane.js
+++ b/x-pack/plugins/ml/public/application/explorer/explorer_swimlane.js
@@ -25,6 +25,7 @@ import { mlChartTooltipService } from '../components/chart_tooltip/chart_tooltip
 import { ALLOW_CELL_RANGE_SELECTION, dragSelect$ } from './explorer_dashboard_service';
 import { DRAG_SELECT_ACTION } from './explorer_constants';
 import { i18n } from '@kbn/i18n';
+import { EMPTY_FIELD_VALUE_LABEL } from '../timeseriesexplorer/components/entity_control/entity_control';
 
 const SCSS = {
   mlDragselectDragging: 'mlDragselectDragging',
@@ -309,6 +310,7 @@ export class ExplorerSwimlane extends React.Component {
       return function(lane) {
         const bucketScore = getBucketScore(lane, time);
         if (bucketScore !== 0) {
+          lane = lane === '' ? EMPTY_FIELD_VALUE_LABEL : lane;
           cellMouseover(this, lane, bucketScore, i, time);
         }
       };
@@ -376,7 +378,7 @@ export class ExplorerSwimlane extends React.Component {
             values: { label: mlEscape(label) },
           });
         } else {
-          return mlEscape(label);
+          return label === '' ? `<i>${EMPTY_FIELD_VALUE_LABEL}</i>` : mlEscape(label);
         }
       })
       .on('click', () => {
@@ -393,7 +395,7 @@ export class ExplorerSwimlane extends React.Component {
                   { skipHeader: true },
                   {
                     label: swimlaneData.fieldName,
-                    value,
+                    value: value === '' ? EMPTY_FIELD_VALUE_LABEL : value,
                     seriesIdentifier: { key: value },
                     valueAccessor: 'fieldName',
                   },
diff --git a/x-pack/plugins/ml/public/application/services/results_service/results_service.js b/x-pack/plugins/ml/public/application/services/results_service/results_service.js
index 4dec066a7f325..b7aa5edc88638 100644
--- a/x-pack/plugins/ml/public/application/services/results_service/results_service.js
+++ b/x-pack/plugins/ml/public/application/services/results_service/results_service.js
@@ -1259,39 +1259,13 @@ export function getRecordMaxScoreByTime(jobId, criteriaFields, earliestMs, lates
       },
       { term: { job_id: jobId } },
     ];
-    const shouldCriteria = [];
 
     _.each(criteriaFields, criteria => {
-      if (criteria.fieldValue.length !== 0) {
-        mustCriteria.push({
-          term: {
-            [criteria.fieldName]: criteria.fieldValue,
-          },
-        });
-      } else {
-        // Add special handling for blank entity field values, checking for either
-        // an empty string or the field not existing.
-        const emptyFieldCondition = {
-          bool: {
-            must: [
-              {
-                term: {},
-              },
-            ],
-          },
-        };
-        emptyFieldCondition.bool.must[0].term[criteria.fieldName] = '';
-        shouldCriteria.push(emptyFieldCondition);
-        shouldCriteria.push({
-          bool: {
-            must_not: [
-              {
-                exists: { field: criteria.fieldName },
-              },
-            ],
-          },
-        });
-      }
+      mustCriteria.push({
+        term: {
+          [criteria.fieldName]: criteria.fieldValue,
+        },
+      });
     });
 
     ml.esSearch({
diff --git a/x-pack/plugins/ml/public/application/timeseriesexplorer/components/entity_control/entity_control.tsx b/x-pack/plugins/ml/public/application/timeseriesexplorer/components/entity_control/entity_control.tsx
index 8911ed53e74d0..7bb0b27472c88 100644
--- a/x-pack/plugins/ml/public/application/timeseriesexplorer/components/entity_control/entity_control.tsx
+++ b/x-pack/plugins/ml/public/application/timeseriesexplorer/components/entity_control/entity_control.tsx
@@ -16,6 +16,7 @@ import {
   EuiFormRow,
   EuiToolTip,
 } from '@elastic/eui';
+import { EuiSelectableOption } from '@elastic/eui/src/components/selectable/selectable_option';
 
 export interface Entity {
   fieldName: string;
@@ -29,15 +30,22 @@ interface EntityControlProps {
   isLoading: boolean;
   onSearchChange: (entity: Entity, queryTerm: string) => void;
   forceSelection: boolean;
-  options: EuiComboBoxOptionOption[];
+  options: Array<EuiComboBoxOptionOption<string>>;
 }
 
 interface EntityControlState {
-  selectedOptions: EuiComboBoxOptionOption[] | undefined;
+  selectedOptions: Array<EuiComboBoxOptionOption<string>> | undefined;
   isLoading: boolean;
-  options: EuiComboBoxOptionOption[] | undefined;
+  options: Array<EuiComboBoxOptionOption<string>> | undefined;
 }
 
+export const EMPTY_FIELD_VALUE_LABEL = i18n.translate(
+  'xpack.ml.timeSeriesExplorer.emptyPartitionFieldLabel.',
+  {
+    defaultMessage: '"" (empty string)',
+  }
+);
+
 export class EntityControl extends Component<EntityControlProps, EntityControlState> {
   inputRef: any;
 
@@ -53,16 +61,18 @@ export class EntityControl extends Component<EntityControlProps, EntityControlSt
 
     const { fieldValue } = entity;
 
-    let selectedOptionsUpdate: EuiComboBoxOptionOption[] | undefined = selectedOptions;
+    let selectedOptionsUpdate: Array<EuiComboBoxOptionOption<string>> | undefined = selectedOptions;
     if (
-      (selectedOptions === undefined && fieldValue.length > 0) ||
+      (selectedOptions === undefined && fieldValue !== null) ||
       (Array.isArray(selectedOptions) &&
         // @ts-ignore
-        selectedOptions[0].label !== fieldValue &&
-        fieldValue.length > 0)
+        selectedOptions[0].value !== fieldValue &&
+        fieldValue !== null)
     ) {
-      selectedOptionsUpdate = [{ label: fieldValue }];
-    } else if (Array.isArray(selectedOptions) && fieldValue.length === 0) {
+      selectedOptionsUpdate = [
+        { label: fieldValue === '' ? EMPTY_FIELD_VALUE_LABEL : fieldValue, value: fieldValue },
+      ];
+    } else if (Array.isArray(selectedOptions) && fieldValue === null) {
       selectedOptionsUpdate = undefined;
     }
 
@@ -84,14 +94,14 @@ export class EntityControl extends Component<EntityControlProps, EntityControlSt
     }
   }
 
-  onChange = (selectedOptions: EuiComboBoxOptionOption[]) => {
+  onChange = (selectedOptions: Array<EuiComboBoxOptionOption<string>>) => {
     const options = selectedOptions.length > 0 ? selectedOptions : undefined;
     this.setState({
       selectedOptions: options,
     });
 
     const fieldValue =
-      Array.isArray(options) && options[0].label.length > 0 ? options[0].label : '';
+      Array.isArray(options) && options[0].value !== null ? options[0].value : null;
     this.props.entityFieldValueChanged(this.props.entity, fieldValue);
   };
 
@@ -103,6 +113,11 @@ export class EntityControl extends Component<EntityControlProps, EntityControlSt
     this.props.onSearchChange(this.props.entity, searchValue);
   };
 
+  renderOption = (option: EuiSelectableOption) => {
+    const { label } = option;
+    return label === EMPTY_FIELD_VALUE_LABEL ? <i>{label}</i> : label;
+  };
+
   render() {
     const { entity, forceSelection } = this.props;
     const { isLoading, options, selectedOptions } = this.state;
@@ -126,6 +141,7 @@ export class EntityControl extends Component<EntityControlProps, EntityControlSt
         onChange={this.onChange}
         onSearchChange={this.onSearchChange}
         isClearable={false}
+        renderOption={this.renderOption}
       />
     );
 
diff --git a/x-pack/plugins/ml/public/application/timeseriesexplorer/timeseries_search_service.ts b/x-pack/plugins/ml/public/application/timeseriesexplorer/timeseries_search_service.ts
index db5ff2ad91910..f973d41ad7754 100644
--- a/x-pack/plugins/ml/public/application/timeseriesexplorer/timeseries_search_service.ts
+++ b/x-pack/plugins/ml/public/application/timeseriesexplorer/timeseries_search_service.ts
@@ -128,7 +128,7 @@ function getChartDetails(
     obj.results.functionLabel = functionLabel;
 
     const blankEntityFields = _.filter(entityFields, entity => {
-      return entity.fieldValue.length === 0;
+      return entity.fieldValue === null;
     });
 
     // Look to see if any of the entity fields have defined values
diff --git a/x-pack/plugins/ml/public/application/timeseriesexplorer/timeseriesexplorer.js b/x-pack/plugins/ml/public/application/timeseriesexplorer/timeseriesexplorer.js
index 1a26540709f34..5e505757dd2aa 100644
--- a/x-pack/plugins/ml/public/application/timeseriesexplorer/timeseriesexplorer.js
+++ b/x-pack/plugins/ml/public/application/timeseriesexplorer/timeseriesexplorer.js
@@ -78,6 +78,7 @@ import {
   processRecordScoreResults,
   getFocusData,
 } from './timeseriesexplorer_utils';
+import { EMPTY_FIELD_VALUE_LABEL } from './components/entity_control/entity_control';
 
 // Used to indicate the chart is being plotted across
 // all partition field values, where the cardinality of the field cannot be
@@ -94,7 +95,7 @@ function getEntityControlOptions(fieldValues) {
   fieldValues.sort();
 
   return fieldValues.map(value => {
-    return { label: value };
+    return { label: value === '' ? EMPTY_FIELD_VALUE_LABEL : value, value };
   });
 }
 
@@ -192,7 +193,7 @@ export class TimeSeriesExplorer extends React.Component {
   getFieldNamesWithEmptyValues = () => {
     const latestEntityControls = this.getControlsForDetector();
     return latestEntityControls
-      .filter(({ fieldValue }) => !fieldValue)
+      .filter(({ fieldValue }) => fieldValue === null)
       .map(({ fieldName }) => fieldName);
   };
 
@@ -249,7 +250,7 @@ export class TimeSeriesExplorer extends React.Component {
     if (operator === '+' && entity.fieldValue !== value) {
       resultValue = value;
     } else if (operator === '-' && entity.fieldValue === value) {
-      resultValue = '';
+      resultValue = null;
     } else {
       return;
     }
@@ -302,7 +303,7 @@ export class TimeSeriesExplorer extends React.Component {
       focusAggregationInterval,
       selectedForecastId,
       modelPlotEnabled,
-      entityControls.filter(entity => entity.fieldValue.length > 0),
+      entityControls.filter(entity => entity.fieldValue !== null),
       searchBounds,
       selectedJob,
       TIME_FIELD_NAME
@@ -576,7 +577,7 @@ export class TimeSeriesExplorer extends React.Component {
         };
 
         const nonBlankEntities = entityControls.filter(entity => {
-          return entity.fieldValue.length > 0;
+          return entity.fieldValue !== null;
         });
 
         if (
@@ -739,7 +740,7 @@ export class TimeSeriesExplorer extends React.Component {
     const overFieldName = get(detector, 'over_field_name');
     const byFieldName = get(detector, 'by_field_name');
     if (partitionFieldName !== undefined) {
-      const partitionFieldValue = get(entitiesState, partitionFieldName, '');
+      const partitionFieldValue = get(entitiesState, partitionFieldName, null);
       entities.push({
         fieldType: 'partition_field',
         fieldName: partitionFieldName,
@@ -747,7 +748,7 @@ export class TimeSeriesExplorer extends React.Component {
       });
     }
     if (overFieldName !== undefined) {
-      const overFieldValue = get(entitiesState, overFieldName, '');
+      const overFieldValue = get(entitiesState, overFieldName, null);
       entities.push({
         fieldType: 'over_field',
         fieldName: overFieldName,
@@ -761,7 +762,7 @@ export class TimeSeriesExplorer extends React.Component {
     // TODO - metric data can be filtered by this field, so should only exclude
     // from filter for the anomaly records.
     if (byFieldName !== undefined && overFieldName === undefined) {
-      const byFieldValue = get(entitiesState, byFieldName, '');
+      const byFieldValue = get(entitiesState, byFieldName, null);
       entities.push({ fieldType: 'by_field', fieldName: byFieldName, fieldValue: byFieldValue });
     }
 
@@ -775,7 +776,7 @@ export class TimeSeriesExplorer extends React.Component {
    */
   getCriteriaFields(detectorIndex, entities) {
     // Only filter on the entity if the field has a value.
-    const nonBlankEntities = entities.filter(entity => entity.fieldValue.length > 0);
+    const nonBlankEntities = entities.filter(entity => entity.fieldValue !== null);
     return [
       {
         fieldName: 'detector_index',
@@ -1150,7 +1151,7 @@ export class TimeSeriesExplorer extends React.Component {
             </EuiFlexItem>
             {entityControls.map(entity => {
               const entityKey = `${entity.fieldName}`;
-              const forceSelection = !hasEmptyFieldValues && !entity.fieldValue;
+              const forceSelection = !hasEmptyFieldValues && entity.fieldValue === null;
               hasEmptyFieldValues = !hasEmptyFieldValues && forceSelection;
               return (
                 <EntityControl
diff --git a/x-pack/plugins/ml/server/models/fields_service/fields_service.ts b/x-pack/plugins/ml/server/models/fields_service/fields_service.ts
index 567c5d2afb7de..6558d0d48ded9 100644
--- a/x-pack/plugins/ml/server/models/fields_service/fields_service.ts
+++ b/x-pack/plugins/ml/server/models/fields_service/fields_service.ts
@@ -6,6 +6,7 @@
 
 import Boom from 'boom';
 import { APICaller } from 'kibana/server';
+import { duration } from 'moment';
 import { parseInterval } from '../../../common/util/parse_interval';
 import { initCardinalityFieldsCache } from './fields_aggs_cache';
 
@@ -16,6 +17,19 @@ import { initCardinalityFieldsCache } from './fields_aggs_cache';
 export function fieldsServiceProvider(callAsCurrentUser: APICaller) {
   const fieldsAggsCache = initCardinalityFieldsCache();
 
+  /**
+   * Caps the time range to the last 90 days if necessary
+   */
+  function getSafeTimeRange(earliestMs: number, latestMs: number): { start: number; end: number } {
+    const capOffsetMs = duration(3, 'months').asMilliseconds();
+    const capRangeStart = latestMs - capOffsetMs;
+
+    return {
+      start: Math.max(earliestMs, capRangeStart),
+      end: latestMs,
+    };
+  }
+
   /**
    * Gets aggregatable fields.
    */
@@ -61,12 +75,14 @@ export function fieldsServiceProvider(callAsCurrentUser: APICaller) {
       return {};
     }
 
+    const { start, end } = getSafeTimeRange(earliestMs, latestMs);
+
     const cachedValues =
       fieldsAggsCache.getValues(
         index,
         timeFieldName,
-        earliestMs,
-        latestMs,
+        start,
+        end,
         'overallCardinality',
         fieldNames
       ) ?? {};
@@ -84,8 +100,8 @@ export function fieldsServiceProvider(callAsCurrentUser: APICaller) {
       {
         range: {
           [timeFieldName]: {
-            gte: earliestMs,
-            lte: latestMs,
+            gte: start,
+            lte: end,
             format: 'epoch_millis',
           },
         },
@@ -130,7 +146,7 @@ export function fieldsServiceProvider(callAsCurrentUser: APICaller) {
       return obj;
     }, {} as { [field: string]: number });
 
-    fieldsAggsCache.updateValues(index, timeFieldName, earliestMs, latestMs, {
+    fieldsAggsCache.updateValues(index, timeFieldName, start, end, {
       overallCardinality: aggResult,
     });
 
@@ -185,15 +201,16 @@ export function fieldsServiceProvider(callAsCurrentUser: APICaller) {
   }
 
   /**
-   * Caps provided time boundaries based on the interval.
-   * @param earliestMs
-   * @param latestMs
-   * @param interval
+   * Caps provided time boundaries based on the interval
    */
-  function getSafeTimeRange(
+  function getSafeTimeRangeForInterval(
+    interval: string,
+    ...timeRange: number[]
+  ): { start: number; end: number };
+  function getSafeTimeRangeForInterval(
+    interval: string,
     earliestMs: number,
-    latestMs: number,
-    interval: string
+    latestMs: number
   ): { start: number; end: number } {
     const maxNumberOfBuckets = 1000;
     const end = latestMs;
@@ -234,7 +251,7 @@ export function fieldsServiceProvider(callAsCurrentUser: APICaller) {
     interval: string | undefined
   ): Promise<{ [key: string]: number }> {
     if (!interval) {
-      throw new Error('Interval is required to retrieve max bucket cardinalities.');
+      throw Boom.badRequest('Interval is required to retrieve max bucket cardinalities.');
     }
 
     const aggregatableFields = await getAggregatableFields(index, fieldNames);
@@ -243,12 +260,17 @@ export function fieldsServiceProvider(callAsCurrentUser: APICaller) {
       return {};
     }
 
+    const { start, end } = getSafeTimeRangeForInterval(
+      interval,
+      ...Object.values(getSafeTimeRange(earliestMs, latestMs))
+    );
+
     const cachedValues =
       fieldsAggsCache.getValues(
         index,
         timeFieldName,
-        earliestMs,
-        latestMs,
+        start,
+        end,
         'maxBucketCardinality',
         fieldNames
       ) ?? {};
@@ -260,8 +282,6 @@ export function fieldsServiceProvider(callAsCurrentUser: APICaller) {
       return cachedValues;
     }
 
-    const { start, end } = getSafeTimeRange(earliestMs, latestMs, interval);
-
     const mustCriteria = [
       {
         range: {
@@ -334,6 +354,10 @@ export function fieldsServiceProvider(callAsCurrentUser: APICaller) {
       return obj;
     }, {} as { [field: string]: number });
 
+    fieldsAggsCache.updateValues(index, timeFieldName, start, end, {
+      maxBucketCardinality: aggResult,
+    });
+
     return {
       ...cachedValues,
       ...aggResult,