diff --git a/services/clsi/app/js/CLSICacheHandler.js b/services/clsi/app/js/CLSICacheHandler.js
index de6f512987..b9415ae3ec 100644
--- a/services/clsi/app/js/CLSICacheHandler.js
+++ b/services/clsi/app/js/CLSICacheHandler.js
@@ -20,6 +20,19 @@ const TIMING_BUCKETS = [
   0, 10, 100, 1000, 2000, 5000, 10000, 15000, 20000, 30000,
 ]
 const MAX_ENTRIES_IN_OUTPUT_TAR = 100
+const OBJECT_ID_REGEX = /^[0-9a-f]{24}$/
+
+/**
+ * @param {string} projectId
+ * @return {{shard: string, url: string}}
+ */
+function getShard(projectId) {
+  // [timestamp 4bytes][random per machine 5bytes][counter 3bytes]
+  //                                          [32bit       4bytes]
+  const last4Bytes = Buffer.from(projectId, 'hex').subarray(8, 12)
+  const idx = last4Bytes.readUInt32BE() % Settings.apis.clsiCache.shards.length
+  return Settings.apis.clsiCache.shards[idx]
+}
 
 /**
  * @param {string} projectId
@@ -29,6 +42,7 @@ const MAX_ENTRIES_IN_OUTPUT_TAR = 100
  * @param {[{path: string}]} outputFiles
  * @param {string} compileGroup
  * @param {Record<string, any>} options
+ * @return {string | undefined}
  */
 function notifyCLSICacheAboutBuild({
   projectId,
@@ -39,14 +53,16 @@ function notifyCLSICacheAboutBuild({
   compileGroup,
   options,
 }) {
-  if (!Settings.apis.clsiCache.enabled) return
+  if (!Settings.apis.clsiCache.enabled) return undefined
+  if (!OBJECT_ID_REGEX.test(projectId)) return undefined
+  const { url, shard } = getShard(projectId)
 
   /**
    * @param {[{path: string}]} files
    */
   const enqueue = files => {
     Metrics.count('clsi_cache_enqueue_files', files.length)
-    fetchNothing(`${Settings.apis.clsiCache.url}/enqueue`, {
+    fetchNothing(`${url}/enqueue`, {
       method: 'POST',
       json: {
         projectId,
@@ -97,6 +113,8 @@ function notifyCLSICacheAboutBuild({
         'build output.tar.gz for clsi cache failed'
       )
     })
+
+  return shard
 }
 
 /**
@@ -155,6 +173,7 @@ async function downloadOutputDotSynctexFromCompileCache(
   outputDir
 ) {
   if (!Settings.apis.clsiCache.enabled) return false
+  if (!OBJECT_ID_REGEX.test(projectId)) return false
 
   const timer = new Metrics.Timer(
     'clsi_cache_download',
@@ -165,7 +184,7 @@ async function downloadOutputDotSynctexFromCompileCache(
   let stream
   try {
     stream = await fetchStream(
-      `${Settings.apis.clsiCache.url}/project/${projectId}/${
+      `${getShard(projectId).url}/project/${projectId}/${
         userId ? `user/${userId}/` : ''
       }build/${editorId}-${buildId}/search/output/output.synctex.gz`,
       {
@@ -205,8 +224,9 @@ async function downloadOutputDotSynctexFromCompileCache(
  */
 async function downloadLatestCompileCache(projectId, userId, compileDir) {
   if (!Settings.apis.clsiCache.enabled) return false
+  if (!OBJECT_ID_REGEX.test(projectId)) return false
 
-  const url = `${Settings.apis.clsiCache.url}/project/${projectId}/${
+  const url = `${getShard(projectId).url}/project/${projectId}/${
     userId ? `user/${userId}/` : ''
   }latest/output/output.tar.gz`
   const timer = new Metrics.Timer(
diff --git a/services/clsi/app/js/CompileController.js b/services/clsi/app/js/CompileController.js
index 87a7db6ec2..c698ee2b75 100644
--- a/services/clsi/app/js/CompileController.js
+++ b/services/clsi/app/js/CompileController.js
@@ -112,12 +112,13 @@ function compile(req, res, next) {
               buildId = error.buildId
             }
 
+            let clsiCacheShard
             if (
               status === 'success' &&
               request.editorId &&
               request.populateClsiCache
             ) {
-              notifyCLSICacheAboutBuild({
+              clsiCacheShard = notifyCLSICacheAboutBuild({
                 projectId: request.project_id,
                 userId: request.user_id,
                 buildId: outputFiles[0].build,
@@ -144,6 +145,7 @@ function compile(req, res, next) {
                 stats,
                 timings,
                 buildId,
+                clsiCacheShard,
                 outputUrlPrefix: Settings.apis.clsi.outputUrlPrefix,
                 outputFiles: outputFiles.map(file => ({
                   url:
diff --git a/services/clsi/config/settings.defaults.js b/services/clsi/config/settings.defaults.js
index 6f16e01a89..17042498db 100644
--- a/services/clsi/config/settings.defaults.js
+++ b/services/clsi/config/settings.defaults.js
@@ -60,9 +60,15 @@ module.exports = {
       }`,
     },
     clsiCache: {
-      enabled: !!process.env.CLSI_CACHE_HOST,
-      url: `http://${process.env.CLSI_CACHE_HOST}:3044`,
-      downloadURL: `http://${process.env.CLSI_CACHE_NGINX_HOST || process.env.CLSI_CACHE_HOST}:8080`,
+      enabled: !!(process.env.CLSI_CACHE_SHARDS || process.env.CLSI_CACHE_HOST),
+      shards: process.env.CLSI_CACHE_SHARDS
+        ? JSON.parse(process.env.CLSI_CACHE_SHARDS)
+        : [
+            {
+              url: `http://${process.env.CLSI_CACHE_HOST}:3044`,
+              shard: 'cache',
+            },
+          ],
     },
   },
 
diff --git a/services/clsi/test/unit/js/CompileControllerTests.js b/services/clsi/test/unit/js/CompileControllerTests.js
index e6d21aed9f..506b5f02dd 100644
--- a/services/clsi/test/unit/js/CompileControllerTests.js
+++ b/services/clsi/test/unit/js/CompileControllerTests.js
@@ -129,6 +129,7 @@ describe('CompileController', function () {
                 url: `${this.Settings.apis.clsi.url}/project/${this.project_id}/build/${file.build}/output/${file.path}`,
                 ...file,
               })),
+              clsiCacheShard: undefined,
             },
           })
           .should.equal(true)
@@ -156,6 +157,7 @@ describe('CompileController', function () {
                 url: `${this.Settings.apis.clsi.url}/project/${this.project_id}/build/${file.build}/output/${file.path}`,
                 ...file,
               })),
+              clsiCacheShard: undefined,
             },
           })
           .should.equal(true)
@@ -203,6 +205,7 @@ describe('CompileController', function () {
               url: `${this.Settings.apis.clsi.url}/project/${this.project_id}/build/${file.build}/output/${file.path}`,
               ...file,
             })),
+            clsiCacheShard: undefined,
           },
         })
       })
@@ -250,6 +253,7 @@ describe('CompileController', function () {
               url: `${this.Settings.apis.clsi.url}/project/${this.project_id}/build/${file.build}/output/${file.path}`,
               ...file,
             })),
+            clsiCacheShard: undefined,
           },
         })
       })
@@ -281,6 +285,7 @@ describe('CompileController', function () {
               buildId: this.buildId,
               stats: this.stats,
               timings: this.timings,
+              clsiCacheShard: undefined,
             },
           })
           .should.equal(true)
@@ -315,6 +320,7 @@ describe('CompileController', function () {
               timings: this.timings,
               // JSON.stringify will omit these undefined values
               buildId: undefined,
+              clsiCacheShard: undefined,
             },
           })
           .should.equal(true)
@@ -348,6 +354,7 @@ describe('CompileController', function () {
               timings: this.timings,
               // JSON.stringify will omit these undefined values
               buildId: undefined,
+              clsiCacheShard: undefined,
             },
           })
           .should.equal(true)
@@ -379,6 +386,7 @@ describe('CompileController', function () {
               timings: this.timings,
               // JSON.stringify will omit these undefined values
               buildId: undefined,
+              clsiCacheShard: undefined,
             },
           })
           .should.equal(true)
diff --git a/services/web/app/src/Features/Compile/ClsiCacheController.js b/services/web/app/src/Features/Compile/ClsiCacheController.js
index 9795fd3ef2..42f037985d 100644
--- a/services/web/app/src/Features/Compile/ClsiCacheController.js
+++ b/services/web/app/src/Features/Compile/ClsiCacheController.js
@@ -110,8 +110,8 @@ async function getLatestBuildFromCache(req, res) {
   const userId = CompileController._getUserIdForCompile(req)
   try {
     const {
-      internal: { location: metaLocation, zone },
-      external: { isUpToDate, allFiles },
+      internal: { location: metaLocation },
+      external: { isUpToDate, allFiles, zone, shard },
     } = await ClsiCacheManager.getLatestBuildFromCache(
       projectId,
       userId,
@@ -153,7 +153,7 @@ async function getLatestBuildFromCache(req, res) {
             size,
             editorId,
           })
-          if (clsiServerId !== 'cache') {
+          if (clsiServerId !== shard) {
             // Enable PDF caching and attempt to download from VM first.
             // (clsi VMs do not have the editorId in the path on disk, omit it).
             Object.assign(f, {
@@ -174,6 +174,7 @@ async function getLatestBuildFromCache(req, res) {
       outputFiles,
       compileGroup,
       clsiServerId,
+      clsiCacheShard: shard,
       pdfDownloadDomain,
       pdfCachingMinChunkSize,
       options,
diff --git a/services/web/app/src/Features/Compile/ClsiCacheHandler.js b/services/web/app/src/Features/Compile/ClsiCacheHandler.js
index 54ebd9e259..76b5d50f12 100644
--- a/services/web/app/src/Features/Compile/ClsiCacheHandler.js
+++ b/services/web/app/src/Features/Compile/ClsiCacheHandler.js
@@ -41,7 +41,7 @@ async function clearCache(projectId, userId) {
   path += '/output'
 
   await Promise.all(
-    Settings.apis.clsiCache.instances.map(async ({ url, zone }) => {
+    Settings.apis.clsiCache.instances.map(async ({ url, shard }) => {
       const u = new URL(url)
       u.pathname = path
       try {
@@ -50,7 +50,7 @@ async function clearCache(projectId, userId) {
           signal: AbortSignal.timeout(15_000),
         })
       } catch (err) {
-        throw OError.tag(err, 'clear clsi-cache', { url, zone })
+        throw OError.tag(err, 'clear clsi-cache', { url, shard })
       }
     })
   )
@@ -64,7 +64,7 @@ async function clearCache(projectId, userId) {
  * @param buildId
  * @param filename
  * @param signal
- * @return {Promise<{size: number, zone: string, location: string, lastModified: Date, allFiles: string[]}>}
+ * @return {Promise<{size: number, zone: string, shard: string, location: string, lastModified: Date, allFiles: string[]}>}
  */
 async function getOutputFile(
   projectId,
@@ -93,7 +93,7 @@ async function getOutputFile(
  * @param userId
  * @param filename
  * @param signal
- * @return {Promise<{size: number, zone: string, location: string, lastModified: Date, allFiles: string[]}>}
+ * @return {Promise<{size: number, zone: string, shard: string, location: string, lastModified: Date, allFiles: string[]}>}
  */
 async function getLatestOutputFile(
   projectId,
@@ -125,7 +125,7 @@ async function getLatestOutputFile(
  * @param userId
  * @param path
  * @param signal
- * @return {Promise<{size: number, zone: string, location: string, lastModified: Date, allFiles: string[]}>}
+ * @return {Promise<{size: number, zone: string, shard: string, location: string, lastModified: Date, allFiles: string[]}>}
  */
 async function getRedirectWithFallback(
   projectId,
@@ -135,7 +135,7 @@ async function getRedirectWithFallback(
 ) {
   // Avoid hitting the same instance first all the time.
   const instances = _.shuffle(Settings.apis.clsiCache.instances)
-  for (const { url, zone } of instances) {
+  for (const { url, shard } of instances) {
     const u = new URL(url)
     u.pathname = path
     try {
@@ -149,6 +149,7 @@ async function getRedirectWithFallback(
       return {
         location,
         zone: headers.get('X-Zone'),
+        shard: headers.get('X-Shard') || 'cache',
         lastModified: new Date(headers.get('X-Last-Modified')),
         size: parseInt(headers.get('X-Content-Length'), 10),
         allFiles: JSON.parse(headers.get('X-All-Files')),
@@ -158,7 +159,7 @@ async function getRedirectWithFallback(
         break // No clsi-cache instance has cached something for this project/user.
       }
       logger.warn(
-        { err, projectId, userId, url, zone },
+        { err, projectId, userId, url, shard },
         'getLatestOutputFile from clsi-cache failed'
       )
       // This clsi-cache instance is down, try the next backend.
@@ -178,18 +179,18 @@ async function getRedirectWithFallback(
  * @param templateId
  * @param templateVersionId
  * @param lastUpdated
- * @param zone
+ * @param shard
  * @param signal
  * @return {Promise<void>}
  */
 async function prepareCacheSource(
   projectId,
   userId,
-  { sourceProjectId, templateId, templateVersionId, lastUpdated, zone, signal }
+  { sourceProjectId, templateId, templateVersionId, lastUpdated, shard, signal }
 ) {
   const url = new URL(
     `/project/${projectId}/user/${userId}/import-from`,
-    Settings.apis.clsiCache.instances.find(i => i.zone === zone).url
+    Settings.apis.clsiCache.instances.find(i => i.shard === shard).url
   )
   try {
     await fetchNothing(url, {
diff --git a/services/web/app/src/Features/Compile/ClsiCacheManager.js b/services/web/app/src/Features/Compile/ClsiCacheManager.js
index 3fe4b987c5..cf0665af56 100644
--- a/services/web/app/src/Features/Compile/ClsiCacheManager.js
+++ b/services/web/app/src/Features/Compile/ClsiCacheManager.js
@@ -1,9 +1,11 @@
+const _ = require('lodash')
 const { NotFoundError } = require('../Errors/Errors')
 const ClsiCacheHandler = require('./ClsiCacheHandler')
 const DocumentUpdaterHandler = require('../DocumentUpdater/DocumentUpdaterHandler')
 const ProjectGetter = require('../Project/ProjectGetter')
 const SplitTestHandler = require('../SplitTests/SplitTestHandler')
 const UserGetter = require('../User/UserGetter')
+const Settings = require('@overleaf/settings')
 
 /**
  * Get the most recent build and metadata
@@ -14,11 +16,11 @@ const UserGetter = require('../User/UserGetter')
  * @param userId
  * @param filename
  * @param signal
- * @return {Promise<{internal: {zone: string, location: string}, external: {isUpToDate: boolean, lastUpdated: Date, size: number, allFiles: string[]}}>}
+ * @return {Promise<{internal: {location: string}, external: {zone: string, shard: string, isUpToDate: boolean, lastUpdated: Date, size: number, allFiles: string[]}}>}
  */
 async function getLatestBuildFromCache(projectId, userId, filename, signal) {
   const [
-    { location, lastModified: lastCompiled, zone, size, allFiles },
+    { location, lastModified: lastCompiled, zone, shard, size, allFiles },
     lastUpdatedInRedis,
     { lastUpdated: lastUpdatedInMongo },
   ] = await Promise.all([
@@ -36,13 +38,14 @@ async function getLatestBuildFromCache(projectId, userId, filename, signal) {
   return {
     internal: {
       location,
-      zone,
     },
     external: {
       isUpToDate,
       lastUpdated,
       size,
       allFiles,
+      shard,
+      zone,
     },
   }
 }
@@ -73,12 +76,11 @@ async function prepareClsiCache(
 
   const signal = AbortSignal.timeout(5_000)
   let lastUpdated
-  let zone = 'b' // populate template data on zone b
+  let shard = _.shuffle(Settings.apis.clsiCache.instances)[0].shard
   if (sourceProjectId) {
     try {
       ;({
-        internal: { zone },
-        external: { lastUpdated },
+        external: { lastUpdated, shard },
       } = await getLatestBuildFromCache(
         sourceProjectId,
         userId,
@@ -95,7 +97,7 @@ async function prepareClsiCache(
       sourceProjectId,
       templateId,
       templateVersionId,
-      zone,
+      shard,
       lastUpdated,
       signal,
     })
diff --git a/services/web/app/src/Features/Compile/ClsiManager.js b/services/web/app/src/Features/Compile/ClsiManager.js
index 2e32aa9622..6f11297248 100644
--- a/services/web/app/src/Features/Compile/ClsiManager.js
+++ b/services/web/app/src/Features/Compile/ClsiManager.js
@@ -207,6 +207,7 @@ async function _sendBuiltRequest(projectId, userId, req, options, callback) {
     stats: compile.stats,
     timings: compile.timings,
     outputUrlPrefix: compile.outputUrlPrefix,
+    clsiCacheShard: compile.clsiCacheShard,
   }
 }
 
@@ -853,6 +854,7 @@ module.exports = {
     'timings',
     'outputUrlPrefix',
     'buildId',
+    'clsiCacheShard',
   ]),
   sendExternalRequest: callbackifyMultiResult(sendExternalRequest, [
     'status',
diff --git a/services/web/app/src/Features/Compile/CompileController.js b/services/web/app/src/Features/Compile/CompileController.js
index 5d2bbcda3e..9fb9d502a4 100644
--- a/services/web/app/src/Features/Compile/CompileController.js
+++ b/services/web/app/src/Features/Compile/CompileController.js
@@ -192,7 +192,8 @@ module.exports = CompileController = {
           stats,
           timings,
           outputUrlPrefix,
-          buildId
+          buildId,
+          clsiCacheShard
         ) => {
           if (error) {
             Metrics.inc('compile-error')
@@ -236,6 +237,7 @@ module.exports = CompileController = {
             outputFilesArchive,
             compileGroup: limits?.compileGroup,
             clsiServerId,
+            clsiCacheShard,
             validationProblems,
             stats,
             timings,
diff --git a/services/web/app/src/Features/Compile/CompileManager.js b/services/web/app/src/Features/Compile/CompileManager.js
index 9b5404865a..974f573815 100644
--- a/services/web/app/src/Features/Compile/CompileManager.js
+++ b/services/web/app/src/Features/Compile/CompileManager.js
@@ -86,6 +86,7 @@ async function compile(projectId, userId, options = {}) {
     timings,
     outputUrlPrefix,
     buildId,
+    clsiCacheShard,
   } = await ClsiManager.promises.sendRequest(projectId, compileAsUser, options)
 
   return {
@@ -98,6 +99,7 @@ async function compile(projectId, userId, options = {}) {
     timings,
     outputUrlPrefix,
     buildId,
+    clsiCacheShard,
   }
 }
 
@@ -184,6 +186,7 @@ module.exports = CompileManager = {
     'timings',
     'outputUrlPrefix',
     'buildId',
+    'clsiCacheShard',
   ]),
 
   stopCompile: callbackify(stopCompile),
diff --git a/services/web/cypress/support/shared/commands/compile.ts b/services/web/cypress/support/shared/commands/compile.ts
index 9f7273c403..44ee9c0805 100644
--- a/services/web/cypress/support/shared/commands/compile.ts
+++ b/services/web/cypress/support/shared/commands/compile.ts
@@ -48,6 +48,7 @@ const compileFromCacheResponse = () => {
     fromCache: true,
     status: 'success',
     clsiServerId: 'foo',
+    clsiCacheShard: 'clsi-cache-zone-b-shard-1',
     compileGroup: 'priority',
     pdfDownloadDomain: 'https://clsi.test-overleaf.com',
     outputFiles: outputFiles(),
@@ -166,10 +167,10 @@ export const waitForCompileOutput = ({
 } = {}) => {
   cy.wait(`@${prefix}-log`)
     .its('request.query.clsiserverid')
-    .should('eq', cached ? 'cache' : 'foo') // straight from cache if cached
+    .should('eq', cached ? 'clsi-cache-zone-b-shard-1' : 'foo') // straight from cache if cached
   cy.wait(`@${prefix}-blg`)
     .its('request.query.clsiserverid')
-    .should('eq', cached ? 'cache' : 'foo') // straight from cache if cached
+    .should('eq', cached ? 'clsi-cache-zone-b-shard-1' : 'foo') // straight from cache if cached
   if (pdf) {
     cy.wait(`@${prefix}-pdf`)
       .its('request.query.clsiserverid')
diff --git a/services/web/frontend/js/features/pdf-preview/util/file-list.ts b/services/web/frontend/js/features/pdf-preview/util/file-list.ts
index 310fbb55fb..a8a37a9e2b 100644
--- a/services/web/frontend/js/features/pdf-preview/util/file-list.ts
+++ b/services/web/frontend/js/features/pdf-preview/util/file-list.ts
@@ -13,6 +13,7 @@ export function buildFileList(
   outputFiles: Map<string, CompileOutputFile>,
   {
     clsiServerId,
+    clsiCacheShard,
     compileGroup,
     outputFilesArchive,
     fromCache = false,
@@ -24,7 +25,7 @@ export function buildFileList(
     const params = new URLSearchParams()
 
     if (fromCache) {
-      params.set('clsiserverid', 'cache')
+      params.set('clsiserverid', clsiCacheShard || 'cache')
     } else if (clsiServerId) {
       params.set('clsiserverid', clsiServerId)
     }
diff --git a/services/web/frontend/js/features/pdf-preview/util/output-files.js b/services/web/frontend/js/features/pdf-preview/util/output-files.js
index 6c93a02368..3ee0dc1180 100644
--- a/services/web/frontend/js/features/pdf-preview/util/output-files.js
+++ b/services/web/frontend/js/features/pdf-preview/util/output-files.js
@@ -17,6 +17,7 @@ export function handleOutputFiles(outputFiles, projectId, data) {
   if (!outputFile) return null
 
   outputFile.editorId = outputFile.editorId || EDITOR_SESSION_ID
+  outputFile.clsiCacheShard = data.clsiCacheShard || 'cache'
 
   // build the URL for viewing the PDF in the preview UI
   const params = new URLSearchParams()
diff --git a/services/web/frontend/js/features/pdf-preview/util/pdf-caching-transport.js b/services/web/frontend/js/features/pdf-preview/util/pdf-caching-transport.js
index 4497b57398..f568c634a4 100644
--- a/services/web/frontend/js/features/pdf-preview/util/pdf-caching-transport.js
+++ b/services/web/frontend/js/features/pdf-preview/util/pdf-caching-transport.js
@@ -116,7 +116,9 @@ export function generatePdfCachingTransportFactory() {
         return (
           u.pathname.endsWith(
             `build/${this.pdfFile.editorId}-${this.pdfFile.build}/output/output.pdf`
-          ) && u.searchParams.get('clsiserverid') === 'cache'
+          ) &&
+          (u.searchParams.get('clsiserverid') === 'cache' ||
+            u.searchParams.get('clsiserverid')?.startsWith('clsi-cache-'))
         )
       }
       const canTryFromCache = err => {
@@ -127,7 +129,7 @@ export function generatePdfCachingTransportFactory() {
       const getOutputPDFURLFromCache = () => {
         if (usesCache(this.url)) return this.url
         const u = new URL(this.url)
-        u.searchParams.set('clsiserverid', 'cache')
+        u.searchParams.set('clsiserverid', this.pdfFile.clsiCacheShard)
         u.pathname = u.pathname.replace(
           /build\/[a-f0-9-]+\//,
           `build/${this.pdfFile.editorId}-${this.pdfFile.build}/`
diff --git a/services/web/types/compile.ts b/services/web/types/compile.ts
index 541d03149c..3038893529 100644
--- a/services/web/types/compile.ts
+++ b/services/web/types/compile.ts
@@ -23,6 +23,7 @@ export type CompileResponseData = {
   outputFiles: CompileOutputFile[]
   compileGroup?: string
   clsiServerId?: string
+  clsiCacheShard?: string
   pdfDownloadDomain?: string
   pdfCachingMinChunkSize: number
   validationProblems: any