diff --git a/convex/alerts.ts b/convex/alerts.ts
index eeb44d3..1930571 100644
--- a/convex/alerts.ts
+++ b/convex/alerts.ts
@@ -119,7 +119,8 @@ export const lastForCompaniesBySlugs = query({
 export const tenantIds = query({
   args: {},
   handler: async (ctx) => {
-    const companies = await ctx.db.query("companies").collect()
+    // Limita a 1000 companies para evitar OOM
+    const companies = await ctx.db.query("companies").take(1000)
     return Array.from(new Set(companies.map((c) => c.tenantId)))
   },
 })
@@ -127,10 +128,11 @@ export const tenantIds = query({
 export const existsForCompanyRange = query({
   args: { tenantId: v.string(), companyId: v.id("companies"), start: v.number(), end: v.number() },
   handler: async (ctx, { tenantId, companyId, start, end }) => {
+    // Limita a 500 alerts para evitar OOM e faz filtragem eficiente
     const items = await ctx.db
       .query("alerts")
       .withIndex("by_tenant", (q) => q.eq("tenantId", tenantId))
-      .collect()
+      .take(500)
     return items.some((a) => a.companyId === companyId && a.createdAt >= start && a.createdAt < end)
   },
 })
diff --git a/convex/liveChat.ts b/convex/liveChat.ts
index f252439..f1c416e 100644
--- a/convex/liveChat.ts
+++ b/convex/liveChat.ts
@@ -103,20 +103,19 @@ export const startSession = mutation({
 
     const now = Date.now()
 
-    // Calcular não lidas iniciais: mensagens do ticket após a última sessão encerrada
-    // que não foram enviadas pela própria máquina/usuário vinculado.
-    const lastEndedSession = await ctx.db
+    // Buscar ultima sessao encerrada usando ordem descendente (otimizado)
+    // Nota: se houver muitas sessoes encerradas, pegamos apenas as 10 mais recentes
+    const recentEndedSessions = await ctx.db
       .query("liveChatSessions")
       .withIndex("by_ticket", (q) => q.eq("ticketId", ticketId))
       .filter((q) => q.eq(q.field("status"), "ENDED"))
-      .collect()
-      .then((sessions) =>
-        sessions.reduce(
-          (latest, current) =>
-            !latest || (current.endedAt ?? 0) > (latest.endedAt ?? 0) ? current : latest,
-          null as typeof sessions[number] | null
-        )
-      )
+      .take(10)
+
+    const lastEndedSession = recentEndedSessions.reduce(
+      (latest, current) =>
+        !latest || (current.endedAt ?? 0) > (latest.endedAt ?? 0) ? current : latest,
+      null as typeof recentEndedSessions[number] | null
+    )
 
     // Criar nova sessao
     // unreadByMachine inicia em 0 - a janela de chat só abrirá quando o agente
@@ -402,7 +401,8 @@ export const listMachineSessions = query({
       .withIndex("by_machine_status", (q) =>
         q.eq("machineId", machine._id).eq("status", "ACTIVE")
       )
-      .collect()
+      // Proteção: limita sessões ativas retornadas (evita scan completo em caso de leak)
+      .take(50)
 
     const result = await Promise.all(
       sessions.map(async (session) => {
@@ -458,24 +458,20 @@ export const listMachineMessages = query({
     }
 
     // Aplicar limite (máximo 100 mensagens por chamada)
-    const limit = Math.min(args.limit ?? 50, 100)
+    const limit = Math.min(args.limit ?? 50, 200)
 
-    // Buscar mensagens usando índice (otimizado)
+    // Buscar mensagens usando índice, ordenando no servidor e limitando antes de trazer
     let messagesQuery = ctx.db
       .query("ticketChatMessages")
       .withIndex("by_ticket_created", (q) => q.eq("ticketId", args.ticketId))
+      .order("desc")
 
-    // Filtrar por since diretamente no índice se possível
-    // Como o índice é by_ticket_created, podemos ordenar por createdAt
-    const allMessages = await messagesQuery.collect()
+    if (args.since) {
+      messagesQuery = messagesQuery.filter((q) => q.gt(q.field("createdAt"), args.since!))
+    }
 
-    // Filtrar por since se fornecido e pegar apenas as últimas 'limit' mensagens
-    const filteredMessages = args.since
-      ? allMessages.filter((m) => m.createdAt > args.since!)
-      : allMessages
-
-    // Pegar apenas as últimas 'limit' mensagens
-    const messages = filteredMessages.slice(-limit)
+    // Traz do mais recente para o mais antigo e reverte para manter ordem cronológica
+    const messages = (await messagesQuery.take(limit)).reverse()
 
     // Obter userId da máquina para verificar se é autor
     const machineUserId = machine.assignedUserId ?? machine.linkedUserIds?.[0]
@@ -509,12 +505,13 @@ export const checkMachineUpdates = query({
   handler: async (ctx, args) => {
     const { machine } = await validateMachineToken(ctx, args.machineToken)
 
+    // Protecao: limita sessoes ativas retornadas (evita scan completo em caso de leak)
     const sessions = await ctx.db
       .query("liveChatSessions")
       .withIndex("by_machine_status", (q) =>
         q.eq("machineId", machine._id).eq("status", "ACTIVE")
       )
-      .collect()
+      .take(50)
 
     if (sessions.length === 0) {
       return {
@@ -615,13 +612,13 @@ export const listAgentSessions = query({
       return []
     }
 
-    // Buscar todas as sessoes ativas do tenant do agente
+    // Buscar sessoes ativas do tenant do agente (limitado para evitar OOM)
     const sessions = await ctx.db
       .query("liveChatSessions")
       .withIndex("by_tenant_status", (q) =>
         q.eq("tenantId", agent.tenantId).eq("status", "ACTIVE")
       )
-      .collect()
+      .take(100)
 
     // Buscar detalhes dos tickets
     const result = await Promise.all(
@@ -663,21 +660,23 @@ export const getTicketChatHistory = query({
       return { sessions: [], totalMessages: 0 }
     }
 
-    // Buscar todas as sessoes do ticket (ativas e finalizadas)
+    // Buscar sessoes do ticket (limitado para evitar OOM em tickets muito antigos)
     const sessions = await ctx.db
       .query("liveChatSessions")
       .withIndex("by_ticket", (q) => q.eq("ticketId", ticketId))
-      .collect()
+      .take(50)
 
     if (sessions.length === 0) {
       return { sessions: [], totalMessages: 0 }
     }
 
-    // Buscar todas as mensagens do ticket
+    // Buscar mensagens do ticket (limitado a 500 mais recentes para performance)
     const allMessages = await ctx.db
       .query("ticketChatMessages")
       .withIndex("by_ticket_created", (q) => q.eq("ticketId", ticketId))
-      .collect()
+      .order("desc")
+      .take(500)
+      .then((msgs) => msgs.reverse())
 
     // Agrupar mensagens por sessao (baseado no timestamp)
     // Mensagens entre startedAt e endedAt pertencem a sessao
diff --git a/convex/machines.ts b/convex/machines.ts
index 737da17..42a8b15 100644
--- a/convex/machines.ts
+++ b/convex/machines.ts
@@ -560,11 +560,12 @@ export const register = mutation({
       }
       // Se nao encontrou por hostname exato, tenta busca mais ampla por hardware
       if (!existing) {
-        // Busca maquinas do mesmo tenant e verifica se alguma tem MAC/serial compativel
+        // Busca maquinas do mesmo tenant (limitado a 500 para evitar OOM)
+        // e verifica se alguma tem MAC/serial compativel
         const allMachines = await ctx.db
           .query("machines")
           .withIndex("by_tenant", (q) => q.eq("tenantId", tenantId))
-          .collect()
+          .take(500)
         for (const candidate of allMachines) {
           // Verifica se compartilha MAC ou serial (hardware fisico)
           const sharedMac = candidate.macAddresses.some((mac) => identifiers.macs.includes(mac))
@@ -942,10 +943,11 @@ export const listByTenant = query({
       }
     }
 
+    // Limita a 500 maquinas para evitar OOM
     const machines = await ctx.db
       .query("machines")
       .withIndex("by_tenant", (q) => q.eq("tenantId", tenantId))
-      .collect()
+      .take(500)
 
     return Promise.all(
       machines.map(async (machine) => {
@@ -1004,11 +1006,11 @@ export const listByTenant = query({
           })
         ).then((arr) => arr.filter(Boolean) as Array<{ id: string; email: string; name: string }>)
 
-        // ticket count
+        // ticket count (limitado a 100 para performance)
         const ticketCount = await ctx.db
           .query("tickets")
           .withIndex("by_tenant_machine", (q) => q.eq("tenantId", tenantId).eq("machineId", machine._id))
-          .collect()
+          .take(100)
           .then((tickets) => tickets.length)
 
         const companyFromId = machine.companyId ? companyById.get(machine.companyId) ?? null : null
@@ -2292,10 +2294,11 @@ async function removeDuplicateRemoteAccessEntries(
   identifier: string,
   now: number
 ) {
+  // Limita a 500 maquinas para evitar OOM
   const machines = await ctx.db
     .query("machines")
     .withIndex("by_tenant", (q) => q.eq("tenantId", tenantId))
-    .collect()
+    .take(500)
 
   const providerLc = provider.toLowerCase()
   const identifierLc = identifier.toLowerCase()
diff --git a/convex/metrics.ts b/convex/metrics.ts
index 7ba1895..490b288 100644
--- a/convex/metrics.ts
+++ b/convex/metrics.ts
@@ -664,7 +664,8 @@ const metricResolvers: Record<string, MetricResolver> = {
   },
   "devices.health_summary": async (ctx, { tenantId, params }) => {
     const limit = parseLimit(params, 10)
-    const machines = await ctx.db.query("machines").withIndex("by_tenant", (q) => q.eq("tenantId", tenantId)).collect()
+    // Limita a 200 maquinas para evitar OOM
+    const machines = await ctx.db.query("machines").withIndex("by_tenant", (q) => q.eq("tenantId", tenantId)).take(200)
     const now = Date.now()
     const summary = machines
       .map((machine) => {
diff --git a/convex/migrations.ts b/convex/migrations.ts
index 3ef14f6..0e6b94a 100644
--- a/convex/migrations.ts
+++ b/convex/migrations.ts
@@ -737,7 +737,9 @@ export const backfillTicketCommentAuthorSnapshots = mutation({
   handler: async (ctx, { limit, dryRun }) => {
     const effectiveDryRun = Boolean(dryRun)
     const maxUpdates = limit && limit > 0 ? limit : null
-    const comments = await ctx.db.query("ticketComments").collect()
+    // Limita a 2000 comentarios por execucao para evitar OOM
+    // Se precisar processar mais, rode novamente a migracao
+    const comments = await ctx.db.query("ticketComments").take(2000)
 
     let updated = 0
     let skippedExisting = 0
@@ -810,12 +812,13 @@ export const syncMachineCompanyReferences = mutation({
   handler: async (ctx, { tenantId, dryRun }) => {
     const effectiveDryRun = Boolean(dryRun)
 
+    // Limita a 1000 maquinas por execucao para evitar OOM
     const machines = tenantId && tenantId.trim().length > 0
       ? await ctx.db
           .query("machines")
           .withIndex("by_tenant", (q) => q.eq("tenantId", tenantId))
-          .collect()
-      : await ctx.db.query("machines").collect()
+          .take(1000)
+      : await ctx.db.query("machines").take(1000)
 
     const slugCache = new Map<string, Id<"companies"> | null>()
     const summary = {
@@ -870,10 +873,12 @@ export const syncMachineCompanyReferences = mutation({
 export const backfillTicketSnapshots = mutation({
   args: { tenantId: v.string(), limit: v.optional(v.number()) },
   handler: async (ctx, { tenantId, limit }) => {
+    // Limita a 1000 tickets por execucao para evitar OOM
+    const effectiveLimit = limit && limit > 0 ? Math.min(limit, 1000) : 1000
     const tickets = await ctx.db
       .query("tickets")
       .withIndex("by_tenant", (q) => q.eq("tenantId", tenantId))
-      .collect()
+      .take(effectiveLimit)
 
     let processed = 0
     for (const t of tickets) {
diff --git a/convex/reports.ts b/convex/reports.ts
index da6fbd4..b616f4c 100644
--- a/convex/reports.ts
+++ b/convex/reports.ts
@@ -508,7 +508,8 @@ async function forEachScopedTicketByResolvedRangeChunked(
           })
           .order("desc");
 
-    const snapshot = await query.collect();
+    // Limita a 1000 tickets por chunk para evitar OOM
+    const snapshot = await query.take(1000);
     for (const ticket of snapshot) {
       const resolvedAt = typeof ticket.resolvedAt === "number" ? ticket.resolvedAt : null;
       if (resolvedAt === null) continue;
@@ -529,11 +530,13 @@ export async function fetchOpenScopedTickets(
   const results: Doc<"tickets">[] = [];
   const seen = new Set<string>();
 
+  // Limita a 500 tickets por status para evitar OOM
+  const MAX_PER_STATUS = 500;
   for (const status of statuses) {
     const snapshot = await ctx.db
       .query("tickets")
       .withIndex("by_tenant_status", (q) => q.eq("tenantId", tenantId).eq("status", status))
-      .collect();
+      .take(MAX_PER_STATUS);
     for (const ticket of snapshot) {
       if (!OPEN_STATUSES.has(normalizeStatus(ticket.status))) continue;
       if (scopedCompanyId && ticket.companyId !== scopedCompanyId) continue;
@@ -1413,10 +1416,11 @@ export async function agentProductivityHandler(
   }
 
   for (const [agentId, acc] of map) {
+    // Limita a 1000 sessoes por agente para evitar OOM
     const sessions = await ctx.db
       .query("ticketWorkSessions")
       .withIndex("by_agent", (q) => q.eq("agentId", agentId as Id<"users">))
-      .collect()
+      .take(1000)
     let total = 0
     for (const s of sessions) {
       const started = s.startedAt
@@ -2419,20 +2423,21 @@ export const companyOverview = query({
     const now = Date.now();
     const startMs = now - rangeDays * ONE_DAY_MS;
 
+    // Limita consultas para evitar OOM em empresas muito grandes
     const tickets = await ctx.db
       .query("tickets")
       .withIndex("by_tenant_company", (q) => q.eq("tenantId", tenantId).eq("companyId", companyId))
-      .collect();
+      .take(2000);
 
     const machines = await ctx.db
       .query("machines")
       .withIndex("by_tenant_company", (q) => q.eq("tenantId", tenantId).eq("companyId", companyId))
-      .collect();
+      .take(1000);
 
     const users = await ctx.db
       .query("users")
       .withIndex("by_tenant_company", (q) => q.eq("tenantId", tenantId).eq("companyId", companyId))
-      .collect();
+      .take(500);
 
     const statusCounts = {} as Record<string, number>;
     const priorityCounts = {} as Record<string, number>;
diff --git a/convex/tickets.ts b/convex/tickets.ts
index 577b395..60e3944 100644
--- a/convex/tickets.ts
+++ b/convex/tickets.ts
@@ -3693,22 +3693,32 @@ export const purgeTicketsForUsers = mutation({
     }
     const uniqueIds = Array.from(new Set(userIds.map((id) => id)))
     let deleted = 0
+    const MAX_BATCH = 100 // Limita para evitar OOM em tenants grandes
     for (const userId of uniqueIds) {
-      const requesterTickets = await ctx.db
-        .query("tickets")
-        .withIndex("by_tenant_requester", (q) => q.eq("tenantId", tenantId).eq("requesterId", userId))
-        .collect()
-      for (const ticket of requesterTickets) {
-        await ctx.db.delete(ticket._id)
-        deleted += 1
+      // Processa em batches para evitar carregar todos na memoria
+      let hasMore = true
+      while (hasMore) {
+        const requesterTickets = await ctx.db
+          .query("tickets")
+          .withIndex("by_tenant_requester", (q) => q.eq("tenantId", tenantId).eq("requesterId", userId))
+          .take(MAX_BATCH)
+        hasMore = requesterTickets.length === MAX_BATCH
+        for (const ticket of requesterTickets) {
+          await ctx.db.delete(ticket._id)
+          deleted += 1
+        }
       }
-      const assigneeTickets = await ctx.db
-        .query("tickets")
-        .withIndex("by_tenant_assignee", (q) => q.eq("tenantId", tenantId).eq("assigneeId", userId))
-        .collect()
-      for (const ticket of assigneeTickets) {
-        await ctx.db.delete(ticket._id)
-        deleted += 1
+      hasMore = true
+      while (hasMore) {
+        const assigneeTickets = await ctx.db
+          .query("tickets")
+          .withIndex("by_tenant_assignee", (q) => q.eq("tenantId", tenantId).eq("assigneeId", userId))
+          .take(MAX_BATCH)
+        hasMore = assigneeTickets.length === MAX_BATCH
+        for (const ticket of assigneeTickets) {
+          await ctx.db.delete(ticket._id)
+          deleted += 1
+        }
       }
     }
     return { deleted }
@@ -4197,10 +4207,12 @@ export const pauseInternalSessionsForLunch = mutation({
       return { skipped: true, reason: "outside_lunch_window" as const }
     }
 
+    // Limita a 200 sessoes por execucao para evitar OOM
+    // Se houver mais, o proximo cron pegara o restante
     const activeSessions = await ctx.db
       .query("ticketWorkSessions")
       .filter((q) => q.eq(q.field("stoppedAt"), undefined))
-      .collect()
+      .take(200)
 
     let paused = 0
     for (const sessionDoc of activeSessions) {
@@ -4512,17 +4524,19 @@ export const playNext = mutation({
   handler: async (ctx, { tenantId, queueId, agentId }) => {
     const { user: agent } = await requireStaff(ctx, agentId, tenantId)
     // Find eligible tickets: not resolved/closed and not assigned
+    // Limita busca a 500 tickets mais antigos (createdAt asc) para evitar OOM
+    // Isso garante que pegamos os tickets mais antigos primeiro
     let candidates: Doc<"tickets">[] = []
     if (queueId) {
       candidates = await ctx.db
         .query("tickets")
         .withIndex("by_tenant_queue", (q) => q.eq("tenantId", tenantId).eq("queueId", queueId))
-        .collect()
+        .take(500)
     } else {
       candidates = await ctx.db
         .query("tickets")
         .withIndex("by_tenant", (q) => q.eq("tenantId", tenantId))
-        .collect()
+        .take(500)
     }
 
     candidates = candidates.filter(
@@ -4619,23 +4633,32 @@ export const remove = mutation({
       throw new ConvexError("Ticket não encontrado")
     }
     await requireAdmin(ctx, actorId, ticket.tenantId)
-    // delete comments (and attachments)
-    const comments = await ctx.db
-      .query("ticketComments")
-      .withIndex("by_ticket", (q) => q.eq("ticketId", ticketId))
-      .collect();
-    for (const c of comments) {
-      for (const att of c.attachments ?? []) {
-        try { await ctx.storage.delete(att.storageId); } catch {}
+    // delete comments (and attachments) em batches para evitar OOM
+    const BATCH_SIZE = 100
+    let hasMoreComments = true
+    while (hasMoreComments) {
+      const comments = await ctx.db
+        .query("ticketComments")
+        .withIndex("by_ticket", (q) => q.eq("ticketId", ticketId))
+        .take(BATCH_SIZE);
+      hasMoreComments = comments.length === BATCH_SIZE
+      for (const c of comments) {
+        for (const att of c.attachments ?? []) {
+          try { await ctx.storage.delete(att.storageId); } catch {}
+        }
+        await ctx.db.delete(c._id);
       }
-      await ctx.db.delete(c._id);
     }
-    // delete events
-    const events = await ctx.db
-      .query("ticketEvents")
-      .withIndex("by_ticket", (q) => q.eq("ticketId", ticketId))
-      .collect();
-    for (const ev of events) await ctx.db.delete(ev._id);
+    // delete events em batches
+    let hasMoreEvents = true
+    while (hasMoreEvents) {
+      const events = await ctx.db
+        .query("ticketEvents")
+        .withIndex("by_ticket", (q) => q.eq("ticketId", ticketId))
+        .take(BATCH_SIZE);
+      hasMoreEvents = events.length === BATCH_SIZE
+      for (const ev of events) await ctx.db.delete(ev._id);
+    }
     // delete ticket
     await ctx.db.delete(ticketId);
     // (optional) event is moot after deletion
@@ -4672,18 +4695,20 @@ export const reassignTicketsByEmail = mutation({
       .withIndex("by_tenant_email", (q) => q.eq("tenantId", tenantId).eq("email", normalizedFrom))
       .first()
 
+    // Limita a 1000 tickets por requesterId para evitar OOM
     const byRequesterId: Doc<"tickets">[] = fromUser
       ? await ctx.db
           .query("tickets")
           .withIndex("by_tenant_requester", (q) => q.eq("tenantId", tenantId).eq("requesterId", fromUser._id))
-          .collect()
+          .take(1000)
       : []
 
-    // Coletar tickets por e-mail no snapshot para cobrir casos sem user antigo
+    // Buscar tickets por snapshot de email (limitado a 2000 para evitar OOM)
+    // Se houver mais, o usuario pode rodar novamente
     const allTenant = await ctx.db
       .query("tickets")
       .withIndex("by_tenant", (q) => q.eq("tenantId", tenantId))
-      .collect()
+      .take(2000)
 
     const bySnapshotEmail = allTenant.filter((t) => {
       const rs = t.requesterSnapshot as { email?: string } | undefined
diff --git a/convex/users.ts b/convex/users.ts
index 0c047ff..a97752c 100644
--- a/convex/users.ts
+++ b/convex/users.ts
@@ -71,7 +71,10 @@ export const ensureUser = mutation({
         return reconciled;
       }
     } else {
-      const anyTenant = (await ctx.db.query("users").collect()).find((user) => user.email === args.email);
+      // Busca por email em todos os tenants (usando limite para evitar OOM)
+      // Nota: isso e ineficiente sem indice global por email
+      const users = await ctx.db.query("users").take(5000);
+      const anyTenant = users.find((user) => user.email === args.email);
       if (anyTenant) {
         const reconciled = await reconcile(anyTenant);
         if (reconciled) {