diff --git a/frontend/src/queries/answers.ts b/frontend/src/queries/answers.ts
index f2d0f9c4..830f3066 100644
--- a/frontend/src/queries/answers.ts
+++ b/frontend/src/queries/answers.ts
@@ -1,16 +1,35 @@
-import type { QuestionId } from "@dwengo-1/common/dist/interfaces/question.ts";
-import { type MaybeRefOrGetter, toValue } from "vue";
-import { useMutation, type UseMutationReturnType, useQuery, type UseQueryReturnType } from "@tanstack/vue-query";
-import { AnswerController, type AnswerResponse, type AnswersResponse } from "@/controllers/answers.ts";
-import type { AnswerData } from "@dwengo-1/common/dist/interfaces/answer.ts";
+import {computed, type MaybeRefOrGetter, toValue} from "vue";
+import {
+    useMutation,
+    type UseMutationReturnType,
+    useQuery,
+    type UseQueryReturnType,
+    useQueryClient,
+} from "@tanstack/vue-query";
+import {
+    AnswerController,
+    type AnswerResponse,
+    type AnswersResponse,
+} from "@/controllers/answers.ts";
+import type { AnswerData } from "@dwengo-1/common/interfaces/answer";
+import type {QuestionId} from "@dwengo-1/common/interfaces/question";
 
-// TODO caching
+/** 🔑 Query keys */
+export function answersQueryKey(questionId: QuestionId, full: boolean): [string, string, number, string, number, boolean] {
+    const loId = questionId.learningObjectIdentifier;
+    return ["answers", loId.hruid, loId.version!, loId.language, questionId.sequenceNumber, full];
+}
+export function answerQueryKey(questionId: QuestionId, sequenceNumber: number): [string, string, number, string, number, number] {
+    const loId = questionId.learningObjectIdentifier;
+    return ["answer", loId.hruid, loId.version!, loId.language, questionId.sequenceNumber, sequenceNumber];
+}
 
 export function useAnswersQuery(
     questionId: MaybeRefOrGetter<QuestionId>,
     full: MaybeRefOrGetter<boolean> = true,
 ): UseQueryReturnType<AnswersResponse, Error> {
     return useQuery({
+        queryKey: computed(() => answersQueryKey(toValue(questionId), toValue(full))),
         queryFn: async () => new AnswerController(toValue(questionId)).getAll(toValue(full)),
         enabled: () => Boolean(toValue(questionId)),
     });
@@ -21,31 +40,69 @@ export function useAnswerQuery(
     sequenceNumber: MaybeRefOrGetter<number>,
 ): UseQueryReturnType<AnswerResponse, Error> {
     return useQuery({
+        queryKey: computed(() => answerQueryKey(toValue(questionId), toValue(sequenceNumber))),
         queryFn: async () => new AnswerController(toValue(questionId)).getBy(toValue(sequenceNumber)),
-        enabled: () => Boolean(toValue(questionId)),
+        enabled: () => Boolean(toValue(questionId)) && Boolean(toValue(sequenceNumber)),
     });
 }
 
 export function useCreateAnswerMutation(
     questionId: MaybeRefOrGetter<QuestionId>,
 ): UseMutationReturnType<AnswerResponse, Error, AnswerData, unknown> {
+    const queryClient = useQueryClient();
+
     return useMutation({
         mutationFn: async (data) => new AnswerController(toValue(questionId)).create(data),
+        onSuccess: async () => {
+            await queryClient.invalidateQueries({
+                queryKey: answersQueryKey(toValue(questionId), true),
+            });
+            await queryClient.invalidateQueries({
+                queryKey: answersQueryKey(toValue(questionId), false),
+            });
+        },
     });
 }
 
 export function useDeleteAnswerMutation(
     questionId: MaybeRefOrGetter<QuestionId>,
 ): UseMutationReturnType<AnswerResponse, Error, number, unknown> {
+    const queryClient = useQueryClient();
+
     return useMutation({
         mutationFn: async (seq) => new AnswerController(toValue(questionId)).remove(seq),
+        onSuccess: async () => {
+            await queryClient.invalidateQueries({
+                queryKey: answersQueryKey(toValue(questionId), true),
+            });
+            await queryClient.invalidateQueries({
+                queryKey: answersQueryKey(toValue(questionId), false),
+            });
+        },
     });
 }
 
 export function useUpdateAnswerMutation(
     questionId: MaybeRefOrGetter<QuestionId>,
 ): UseMutationReturnType<AnswerResponse, Error, { answerData: AnswerData; seq: number }, unknown> {
+    const queryClient = useQueryClient();
+
     return useMutation({
-        mutationFn: async (data, seq) => new AnswerController(toValue(questionId)).update(seq, data),
+        mutationFn: async ({ answerData, seq }) =>
+            new AnswerController(toValue(questionId)).update(seq, answerData),
+        onSuccess: async (_, { seq }) => {
+            await queryClient.invalidateQueries({
+                queryKey: answerQueryKey(toValue(questionId), seq),
+            });
+            await queryClient.invalidateQueries({
+                queryKey: answersQueryKey(toValue(questionId), true),
+            });
+            await queryClient.invalidateQueries({
+                queryKey: answersQueryKey(toValue(questionId), true),
+            });
+            await queryClient.invalidateQueries({
+                queryKey: answersQueryKey(toValue(questionId), false),
+            });
+        },
     });
 }
diff --git a/frontend/src/queries/questions.ts b/frontend/src/queries/questions.ts
index b69164a4..66f1492f 100644
--- a/frontend/src/queries/questions.ts
+++ b/frontend/src/queries/questions.ts
@@ -14,12 +14,12 @@ export function questionsQueryKey(
     loId: LearningObjectIdentifierDTO,
     full: boolean,
 ): [string, string, number, string, boolean] {
-    return ["questions", loId.hruid, loId.version, loId.language, full];
+    return ["questions", loId.hruid, loId.version!, loId.language, full];
 }
 
 export function questionQueryKey(questionId: QuestionId): [string, string, number, string, number] {
     const loId = questionId.learningObjectIdentifier;
-    return ["question", loId.hruid, loId.version, loId.language, questionId.sequenceNumber];
+    return ["question", loId.hruid, loId.version!, loId.language, questionId.sequenceNumber];
 }
 
 export function useQuestionsQuery(
@@ -39,7 +39,7 @@ export function useQuestionQuery(
     const loId = toValue(questionId).learningObjectIdentifier;
     const sequenceNumber = toValue(questionId).sequenceNumber;
     return useQuery({
-        queryKey: computed(() => questionQueryKey(loId, sequenceNumber)),
+        queryKey: computed(() => questionQueryKey(toValue(questionId))),
         queryFn: async () => new QuestionController(loId).getBy(sequenceNumber),
         enabled: () => Boolean(toValue(questionId)),
     });
@@ -55,6 +55,7 @@ export function useCreateQuestionMutation(
         onSuccess: async () => {
             await queryClient.invalidateQueries({ queryKey: questionsQueryKey(toValue(loId), true) });
             await queryClient.invalidateQueries({ queryKey: questionsQueryKey(toValue(loId), false) });
+            await queryClient.invalidateQueries({ queryKey: ["answers"] });
         },
     });
 }
@@ -88,6 +89,8 @@ export function useDeleteQuestionMutation(
             await queryClient.invalidateQueries({ queryKey: questionsQueryKey(toValue(loId), true) });
             await queryClient.invalidateQueries({ queryKey: questionsQueryKey(toValue(loId), false) });
             await queryClient.invalidateQueries({ queryKey: questionQueryKey(toValue(questionId)) });
+            await queryClient.invalidateQueries({ queryKey: ["answers"] });
+            await queryClient.invalidateQueries({ queryKey: ["answer"] });
         },
     });
 }
diff --git a/frontend/src/queries/teacher-invitations.ts b/frontend/src/queries/teacher-invitations.ts
index 59357c32..3e650343 100644
--- a/frontend/src/queries/teacher-invitations.ts
+++ b/frontend/src/queries/teacher-invitations.ts
@@ -1,36 +1,56 @@
-import { useMutation, useQuery, type UseMutationReturnType, type UseQueryReturnType } from "@tanstack/vue-query";
-import { computed, toValue } from "vue";
+import {
+    useMutation,
+    useQuery,
+    useQueryClient,
+    type UseMutationReturnType,
+    type UseQueryReturnType,
+} from "@tanstack/vue-query";
+import { toValue } from "vue";
 import type { MaybeRefOrGetter } from "vue";
 import {
     TeacherInvitationController,
     type TeacherInvitationResponse,
     type TeacherInvitationsResponse,
-} from "@/controllers/teacher-invitations.ts";
+} from "@/controllers/teacher-invitations";
 import type { TeacherInvitationData } from "@dwengo-1/common/interfaces/teacher-invitation";
-import type { TeacherDTO } from "@dwengo-1/common/interfaces/teacher";
 
 const controller = new TeacherInvitationController();
 
+/** 🔑 Query keys */
+export function teacherInvitationsSentQueryKey(username: string): [string, string, string] {
+    return ["teacher-invitations", "sent", username];
+}
+
+export function teacherInvitationsReceivedQueryKey(username: string): [string, string, string] {
+    return ["teacher-invitations", "received", username ];
+}
+
+export function teacherInvitationQueryKey(data: TeacherInvitationData): [string, string, string, string] {
+    return ["teacher-invitation", data.sender, data.receiver, data.class];
+}
+
 /**
-    All the invitations the teacher sent
-**/
+ * All the invitations the teacher sent
+ */
 export function useTeacherInvitationsSentQuery(
     username: MaybeRefOrGetter<string | undefined>,
 ): UseQueryReturnType<TeacherInvitationsResponse, Error> {
     return useQuery({
-        queryFn: computed(async () => controller.getAll(toValue(username), true)),
+        queryKey: teacherInvitationsSentQueryKey(toValue(username)!),
+        queryFn: async () => controller.getAll(toValue(username)!, true),
         enabled: () => Boolean(toValue(username)),
     });
 }
 
 /**
-    All the pending invitations sent to this teacher
+ * All the pending invitations sent to this teacher
  */
 export function useTeacherInvitationsReceivedQuery(
     username: MaybeRefOrGetter<string | undefined>,
 ): UseQueryReturnType<TeacherInvitationsResponse, Error> {
     return useQuery({
-        queryFn: computed(async () => controller.getAll(toValue(username), false)),
+        queryKey: teacherInvitationsReceivedQueryKey(toValue(username)!),
+        queryFn: async () => controller.getAll(toValue(username)!, false),
         enabled: () => Boolean(toValue(username)),
     });
 }
@@ -39,7 +59,8 @@ export function useTeacherInvitationQuery(
     data: MaybeRefOrGetter<TeacherInvitationData | undefined>,
 ): UseQueryReturnType<TeacherInvitationResponse, Error> {
     return useQuery({
-        queryFn: computed(async () => controller.getBy(toValue(data))),
+        queryKey: teacherInvitationQueryKey(toValue(data)!),
+        queryFn: async () => controller.getBy(toValue(data)!),
         enabled: () => Boolean(toValue(data)),
     });
 }
@@ -47,32 +68,68 @@ export function useTeacherInvitationQuery(
 export function useCreateTeacherInvitationMutation(): UseMutationReturnType<
     TeacherInvitationResponse,
     Error,
-    TeacherDTO,
+    TeacherInvitationData,
     unknown
 > {
+    const queryClient = useQueryClient();
+
     return useMutation({
-        mutationFn: async (data: TeacherInvitationData) => controller.create(data),
+        mutationFn: async (data) => controller.create(data),
+        onSuccess: async (_, data) => {
+            await queryClient.invalidateQueries({
+                queryKey: teacherInvitationsSentQueryKey(data.sender),
+            });
+            await queryClient.invalidateQueries({
+                queryKey: teacherInvitationsReceivedQueryKey(data.receiver),
+            });
+        },
     });
 }
 
 export function useRespondTeacherInvitationMutation(): UseMutationReturnType<
     TeacherInvitationResponse,
     Error,
-    TeacherDTO,
+    TeacherInvitationData,
     unknown
 > {
+    const queryClient = useQueryClient();
+
     return useMutation({
-        mutationFn: async (data: TeacherInvitationData) => controller.respond(data),
+        mutationFn: async (data) => controller.respond(data),
+        onSuccess: async (_, data) => {
+            await queryClient.invalidateQueries({
+                queryKey: teacherInvitationsSentQueryKey(data.sender),
+            });
+            await queryClient.invalidateQueries({
+                queryKey: teacherInvitationsReceivedQueryKey(data.receiver),
+            });
+            await queryClient.invalidateQueries({
+                queryKey: teacherInvitationQueryKey(data),
+            });
+        },
     });
 }
 
 export function useDeleteTeacherInvitationMutation(): UseMutationReturnType<
     TeacherInvitationResponse,
     Error,
-    TeacherDTO,
+    TeacherInvitationData,
     unknown
 > {
+    const queryClient = useQueryClient();
+
     return useMutation({
-        mutationFn: async (data: TeacherInvitationData) => controller.remove(data),
+        mutationFn: async (data) => controller.remove(data),
+        onSuccess: async (_, data) => {
+            await queryClient.invalidateQueries({
+                queryKey: teacherInvitationsSentQueryKey(data.sender),
+            });
+            await queryClient.invalidateQueries({
+                queryKey: teacherInvitationsReceivedQueryKey(data.receiver),
+            });
+            await queryClient.invalidateQueries({
+                queryKey: teacherInvitationQueryKey(data),
+            });
+        },
     });
 }
diff --git a/frontend/src/queries/teachers.ts b/frontend/src/queries/teachers.ts
index 3e77f819..59da84f4 100644
--- a/frontend/src/queries/teachers.ts
+++ b/frontend/src/queries/teachers.ts
@@ -137,7 +137,7 @@ export function useUpdateJoinRequestMutation(): UseMutationReturnType<
         mutationFn: async ({ teacherUsername, classId, studentUsername, accepted }) =>
             teacherController.updateStudentJoinRequest(teacherUsername, classId, studentUsername, accepted),
         onSuccess: async (deletedJoinRequest) => {
-            const username = deletedJoinRequest.request.requester;
+            const username = deletedJoinRequest.request.requester.username;
             const classId = deletedJoinRequest.request.class;
             await queryClient.invalidateQueries({ queryKey: studentJoinRequestsQueryKey(username) });
             await queryClient.invalidateQueries({ queryKey: studentJoinRequestQueryKey(username, classId) });
diff --git a/frontend/src/queries/themes.ts b/frontend/src/queries/themes.ts
index c3be25ae..ee197d14 100644
--- a/frontend/src/queries/themes.ts
+++ b/frontend/src/queries/themes.ts
@@ -1,7 +1,7 @@
 import { useQuery, type UseQueryReturnType } from "@tanstack/vue-query";
 import { type MaybeRefOrGetter, toValue } from "vue";
-import type { Theme } from "@dwengo-1/interfaces/theme";
 import { getThemeController } from "@/controllers/controllers.ts";
+import type {Theme} from "@dwengo-1/common/interfaces/theme";
 
 const themeController = getThemeController();