diff --git a/src/plugins/vis_type_timeseries/common/types/vis_data.ts b/src/plugins/vis_type_timeseries/common/types/vis_data.ts
index 15755a5bb668a..fb3e0db82f188 100644
--- a/src/plugins/vis_type_timeseries/common/types/vis_data.ts
+++ b/src/plugins/vis_type_timeseries/common/types/vis_data.ts
@@ -46,7 +46,7 @@ export interface PanelData {
   error?: string;
 }
 
-export type PanelDataArray = [number | undefined, number | string | null];
+export type PanelDataArray = [number | undefined | string, number | string | null];
 
 export interface Annotation {
   key: number;
diff --git a/src/plugins/vis_type_timeseries/public/application/components/lib/get_interval.ts b/src/plugins/vis_type_timeseries/public/application/components/lib/get_interval.ts
index 082a3978f29ed..4b232af299a19 100644
--- a/src/plugins/vis_type_timeseries/public/application/components/lib/get_interval.ts
+++ b/src/plugins/vis_type_timeseries/public/application/components/lib/get_interval.ts
@@ -77,8 +77,12 @@ export const getInterval = (visData: TimeseriesVisData, model: TimeseriesVisPara
   ) as PanelData[];
 
   return series.reduce((currentInterval, item) => {
-    if (item.data.length > 1) {
-      const seriesInterval = item.data[1][0]! - item.data[0][0]!;
+    if (
+      item.data.length > 1 &&
+      typeof item.data[1][0] === 'number' &&
+      typeof item.data[0][0] === 'number'
+    ) {
+      const seriesInterval = item.data[1][0] - item.data[0][0];
       if (!currentInterval || seriesInterval < currentInterval) return seriesInterval;
     }
     return currentInterval;
diff --git a/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/get_splits.ts b/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/get_splits.ts
index 68af9d7bad970..6e33d8ab07a42 100644
--- a/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/get_splits.ts
+++ b/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/get_splits.ts
@@ -27,7 +27,14 @@ interface SplittedData<TMeta extends BaseMeta = BaseMeta> {
   color: string;
   meta: TMeta;
   timeseries: {
-    buckets: Array<Record<string, unknown> & { key: string }>;
+    buckets: [
+      {
+        [s: string]: {
+          // should be typed
+          values: Record<string, unknown>;
+        };
+      } & { key: string | number }
+    ];
   };
 }
 
diff --git a/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/map_empty_to_zero.ts b/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/map_empty_to_zero.ts
index 8b04251411134..a035d566d130e 100644
--- a/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/map_empty_to_zero.ts
+++ b/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/map_empty_to_zero.ts
@@ -10,15 +10,16 @@
 import { getAggValue } from './get_agg_value';
 import { METRIC_TYPES } from '../../../../../data/common';
 import type { Metric } from '../../../../common/types';
+import type { PanelDataArray } from '../../../../common/types/vis_data';
 
 export const mapEmptyToZero = (
   metric: Metric,
   buckets: Array<
     {
-      key: number;
+      key: number | string;
     } & Record<string, unknown>
   >
-) => {
+): PanelDataArray[] => {
   // Metric types where an empty set equals `zero`
   const isSettableToZero = [
     METRIC_TYPES.COUNT,
diff --git a/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/timestamp.ts b/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/timestamp.ts
index 4388de43667dd..7374b483aeec8 100644
--- a/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/timestamp.ts
+++ b/src/plugins/vis_type_timeseries/server/lib/vis_data/helpers/timestamp.ts
@@ -38,7 +38,7 @@ export function getLastSeriesTimestamp(seriesGroup: Array<PanelSeries['series']>
       if (lastValue) {
         const [dataLastTimestamp] = lastValue;
 
-        if (typeof dataLastTimestamp !== 'undefined') {
+        if (typeof dataLastTimestamp === 'number') {
           lastTimestamp = Math.max(dataLastTimestamp, lastTimestamp ?? dataLastTimestamp);
         }
       }
diff --git a/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/percentile.ts b/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/percentile.ts
index 4004501c2e015..6514267ee0ec3 100644
--- a/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/percentile.ts
+++ b/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/percentile.ts
@@ -12,7 +12,7 @@ import { toPercentileNumber } from '../../../../../common/to_percentile_number';
 import { METRIC_TYPES } from '../../../../../common/enums';
 
 import type { TableResponseProcessorsFunction } from './types';
-import { PanelDataArray } from '../../../../../common/types/vis_data';
+import type { PanelDataArray } from '../../../../../common/types/vis_data';
 
 export const percentile: TableResponseProcessorsFunction = ({
   bucket,
@@ -36,7 +36,7 @@ export const percentile: TableResponseProcessorsFunction = ({
     const lastPercentile = last(metric.percentiles)?.value ?? 0;
     const percentileKey = toPercentileNumber(lastPercentile);
     const data = split.timeseries.buckets.map((b) => [
-      Number(b.key),
+      b.key,
       b[metric.id].values[percentileKey],
     ]) as PanelDataArray[];
 
diff --git a/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/percentile_rank.ts b/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/percentile_rank.ts
index 0e1d4effe4c2f..73e177e21e756 100644
--- a/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/percentile_rank.ts
+++ b/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/percentile_rank.ts
@@ -12,7 +12,7 @@ import { toPercentileNumber } from '../../../../../common/to_percentile_number';
 import { METRIC_TYPES } from '../../../../../common/enums';
 
 import type { TableResponseProcessorsFunction } from './types';
-import { PanelDataArray } from '../../../../../common/types/vis_data';
+import type { PanelDataArray } from '../../../../../common/types/vis_data';
 
 export const percentileRank: TableResponseProcessorsFunction = ({
   bucket,
@@ -37,7 +37,7 @@ export const percentileRank: TableResponseProcessorsFunction = ({
     const lastPercentileNumber = toPercentileNumber(lastRankValue);
 
     const data = split.timeseries.buckets.map((b) => [
-      Number(b.key),
+      b.key,
       getAggValue(b, {
         ...metric,
         value: lastPercentileNumber,
diff --git a/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/std_sibling.ts b/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/std_sibling.ts
index b08bee7558b81..414108291a24f 100644
--- a/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/std_sibling.ts
+++ b/src/plugins/vis_type_timeseries/server/lib/vis_data/response_processors/table/std_sibling.ts
@@ -26,7 +26,7 @@ export const stdSibling: TableResponseProcessorsFunction = ({
   const fakeResp = { aggregations: bucket };
   (await getSplits(fakeResp, panel, series, meta, extractFields)).forEach((split) => {
     const data: PanelDataArray[] = split.timeseries.buckets.map((b) => {
-      return [Number(b.key), getSiblingAggValue(split, metric)];
+      return [b.key, getSiblingAggValue(split, metric)];
     });
 
     results.push({