diff --git a/backend/src/graphql/models/Decay.ts b/backend/src/graphql/models/Decay.ts
index 17ee8fbac..860580e8f 100644
--- a/backend/src/graphql/models/Decay.ts
+++ b/backend/src/graphql/models/Decay.ts
@@ -15,13 +15,6 @@ export class Decay {
     }
   }
 
-  static async getDecayStartBlock(): Promise<Transaction | undefined> {
-    if (!this.decayStartBlockTransaction) {
-      this.decayStartBlockTransaction = await Transaction.getDecayStartBlock()
-    }
-    return this.decayStartBlockTransaction
-  }
-
   @Field(() => Number)
   balance: number
 
@@ -38,6 +31,4 @@ export class Decay {
 
   @Field(() => Int, { nullable: true })
   decayStartBlock?: string
-
-  static decayStartBlockTransaction: Transaction | undefined
 }
diff --git a/backend/src/graphql/resolvers/BalanceResolver.ts b/backend/src/graphql/resolvers/BalanceResolver.ts
index 1d1afaa2a..4c83bbbcd 100644
--- a/backend/src/graphql/resolvers/BalanceResolver.ts
+++ b/backend/src/graphql/resolvers/BalanceResolver.ts
@@ -2,9 +2,10 @@
 /* eslint-disable @typescript-eslint/explicit-module-boundary-types */
 
 import { Resolver, Query, Ctx, Authorized } from 'type-graphql'
+import { getCustomRepository } from 'typeorm'
 import { Balance } from '../models/Balance'
-import { User as dbUser } from '../../typeorm/entity/User'
-import { Balance as dbBalance } from '../../typeorm/entity/Balance'
+import { BalanceRepository } from '../../typeorm/repository/Balance'
+import { UserRepository } from '../../typeorm/repository/User'
 import { calculateDecay } from '../../util/decay'
 import { roundFloorFrom4 } from '../../util/round'
 
@@ -14,8 +15,11 @@ export class BalanceResolver {
   @Query(() => Balance)
   async balance(@Ctx() context: any): Promise<Balance> {
     // load user and balance
-    const userEntity = await dbUser.findByPubkeyHex(context.pubKey)
-    const balanceEntity = await dbBalance.findByUser(userEntity.id)
+    const balanceRepository = getCustomRepository(BalanceRepository)
+    const userRepository = getCustomRepository(UserRepository)
+
+    const userEntity = await userRepository.findByPubkeyHex(context.pubKey)
+    const balanceEntity = await balanceRepository.findByUser(userEntity.id)
     let balance: Balance
     const now = new Date()
     if (balanceEntity) {
diff --git a/backend/src/graphql/resolvers/GdtResolver.ts b/backend/src/graphql/resolvers/GdtResolver.ts
index 0e9af5ad6..8ea006313 100644
--- a/backend/src/graphql/resolvers/GdtResolver.ts
+++ b/backend/src/graphql/resolvers/GdtResolver.ts
@@ -2,11 +2,12 @@
 /* eslint-disable @typescript-eslint/explicit-module-boundary-types */
 
 import { Resolver, Query, Args, Ctx, Authorized } from 'type-graphql'
+import { getCustomRepository } from 'typeorm'
 import CONFIG from '../../config'
 import { GdtEntryList } from '../models/GdtEntryList'
 import { GdtTransactionSessionIdInput } from '../inputs/GdtInputs'
 import { apiGet } from '../../apis/HttpRequest'
-import { User as dbUser } from '../../typeorm/entity/User'
+import { UserRepository } from '../../typeorm/repository/User'
 
 @Resolver()
 export class GdtResolver {
@@ -19,7 +20,8 @@ export class GdtResolver {
     @Ctx() context: any,
   ): Promise<GdtEntryList> {
     // load user
-    const userEntity = await dbUser.findByPubkeyHex(context.pubKey)
+    const userRepository = getCustomRepository(UserRepository)
+    const userEntity = await userRepository.findByPubkeyHex(context.pubKey)
 
     const resultGDT = await apiGet(
       `${CONFIG.GDT_API_URL}/GdtEntries/listPerEmailApi/${userEntity.email}/${currentPage}/${pageSize}/${order}`,
diff --git a/backend/src/graphql/resolvers/TransactionResolver.ts b/backend/src/graphql/resolvers/TransactionResolver.ts
index 3762cccee..cd07a94f5 100644
--- a/backend/src/graphql/resolvers/TransactionResolver.ts
+++ b/backend/src/graphql/resolvers/TransactionResolver.ts
@@ -2,12 +2,13 @@
 /* eslint-disable @typescript-eslint/explicit-module-boundary-types */
 
 import { Resolver, Query, Args, Authorized, Ctx, Mutation } from 'type-graphql'
+import { getCustomRepository } from 'typeorm'
 import CONFIG from '../../config'
 import { TransactionList } from '../models/Transaction'
 import { TransactionListInput, TransactionSendArgs } from '../inputs/TransactionInput'
 import { apiGet, apiPost } from '../../apis/HttpRequest'
-import { User as dbUser } from '../../typeorm/entity/User'
-import { Balance as dbBalance } from '../../typeorm/entity/Balance'
+import { BalanceRepository } from '../../typeorm/repository/Balance'
+import { UserRepository } from '../../typeorm/repository/User'
 import listTransactions from './listTransactions'
 import { roundFloorFrom4 } from '../../util/round'
 import { calculateDecay } from '../../util/decay'
@@ -25,7 +26,8 @@ export class TransactionResolver {
     if (!result.success) throw new Error(result.data)
 
     // load user
-    const userEntity = await dbUser.findByPubkeyHex(result.data.user.public_hex)
+    const userRepository = getCustomRepository(UserRepository)
+    const userEntity = await userRepository.findByPubkeyHex(result.data.user.public_hex)
 
     const transactions = await listTransactions(firstPage, items, order, userEntity)
 
@@ -37,7 +39,8 @@ export class TransactionResolver {
     transactions.gdtSum = resultGDTSum.data.sum
 
     // get balance
-    const balanceEntity = await dbBalance.findByUser(userEntity.id)
+    const balanceRepository = getCustomRepository(BalanceRepository)
+    const balanceEntity = await balanceRepository.findByUser(userEntity.id)
     if (balanceEntity) {
       const now = new Date()
       transactions.balance = roundFloorFrom4(balanceEntity.amount)
diff --git a/backend/src/graphql/resolvers/listTransactions.ts b/backend/src/graphql/resolvers/listTransactions.ts
index 1de7d7dcc..bf84e17d4 100644
--- a/backend/src/graphql/resolvers/listTransactions.ts
+++ b/backend/src/graphql/resolvers/listTransactions.ts
@@ -1,8 +1,11 @@
+import { getCustomRepository } from 'typeorm'
 import { User as dbUser } from '../../typeorm/entity/User'
+import { UserRepository } from '../../typeorm/repository/User'
 import { TransactionList, Transaction } from '../models/Transaction'
 import { UserTransaction as dbUserTransaction } from '../../typeorm/entity/UserTransaction'
+import { UserTransactionRepository } from '../../typeorm/repository/UserTransaction'
 import { Transaction as dbTransaction } from '../../typeorm/entity/Transaction'
-import { Decay } from '../models/Decay'
+import { TransactionRepository } from '../../typeorm/repository/Transaction'
 import { calculateDecayWithInterval } from '../../util/decay'
 import { roundFloorFrom4 } from '../../util/round'
 
@@ -20,20 +23,8 @@ async function calculateAndAddDecayTransactions(
     transactionIds.push(userTransaction.transactionId)
   })
 
-  const transactions = await dbTransaction
-    .createQueryBuilder('transaction')
-    .where('transaction.id IN (:...transactions)', { transactions: transactionIds })
-    .leftJoinAndSelect(
-      'transaction.transactionSendCoin',
-      'transactionSendCoin',
-      // 'transactionSendCoin.transaction_id = transaction.id',
-    )
-    .leftJoinAndSelect(
-      'transaction.transactionCreation',
-      'transactionCreation',
-      // 'transactionSendCoin.transaction_id = transaction.id',
-    )
-    .getMany()
+  const transactionRepository = getCustomRepository(TransactionRepository)
+  const transactions = await transactionRepository.joinFullTransactionsByIds(transactionIds)
 
   const transactionIndiced: dbTransaction[] = []
   transactions.forEach((transaction: dbTransaction) => {
@@ -46,9 +37,10 @@ async function calculateAndAddDecayTransactions(
   // remove duplicates
   // https://stackoverflow.com/questions/1960473/get-all-unique-values-in-a-javascript-array-remove-duplicates
   const involvedUsersUnique = involvedUserIds.filter((v, i, a) => a.indexOf(v) === i)
-  const userIndiced = await dbUser.getUsersIndiced(involvedUsersUnique)
+  const userRepository = getCustomRepository(UserRepository)
+  const userIndiced = await userRepository.getUsersIndiced(involvedUsersUnique)
 
-  const decayStartTransaction = await Decay.getDecayStartBlock()
+  const decayStartTransaction = await transactionRepository.findDecayStartBlock()
 
   for (let i = 0; i < userTransactions.length; i++) {
     const userTransaction = userTransactions[i]
@@ -163,7 +155,8 @@ export default async function listTransactions(
   if (offset && order === 'ASC') {
     offset--
   }
-  let [userTransactions, userTransactionsCount] = await dbUserTransaction.findByUserPaged(
+  const userTransactionRepository = getCustomRepository(UserTransactionRepository)
+  let [userTransactions, userTransactionsCount] = await userTransactionRepository.findByUserPaged(
     user.id,
     limit,
     offset,
diff --git a/backend/src/typeorm/entity/Balance.ts b/backend/src/typeorm/entity/Balance.ts
index 23b21de78..c1ca359f1 100644
--- a/backend/src/typeorm/entity/Balance.ts
+++ b/backend/src/typeorm/entity/Balance.ts
@@ -16,8 +16,4 @@ export class Balance extends BaseEntity {
 
   @Column({ type: 'bigint' })
   amount: number
-
-  static findByUser(userId: number): Promise<Balance | undefined> {
-    return this.createQueryBuilder('balance').where('balance.userId = :userId', { userId }).getOne()
-  }
 }
diff --git a/backend/src/typeorm/entity/Group.ts b/backend/src/typeorm/entity/Group.ts
deleted file mode 100644
index 6694ea742..000000000
--- a/backend/src/typeorm/entity/Group.ts
+++ /dev/null
@@ -1,25 +0,0 @@
-/* import { Entity, PrimaryGeneratedColumn, Column, OneToMany } from "typeorm";
-import { User } from "./User"
-
-@Entity()
-export class Group {
-
-    @PrimaryGeneratedColumn()
-    id: number;
-
-    @Column()
-    alias: string;
-
-    @Column()
-    name: string;
-
-    @Column()
-    url: string;
-
-    @Column()
-    description: string;
-
-    @OneToMany(type => User, user => user.group)
-    users: User[];
-
-} */
diff --git a/backend/src/typeorm/entity/Transaction.ts b/backend/src/typeorm/entity/Transaction.ts
index d8b87828c..53dce4d08 100644
--- a/backend/src/typeorm/entity/Transaction.ts
+++ b/backend/src/typeorm/entity/Transaction.ts
@@ -27,19 +27,4 @@ export class Transaction extends BaseEntity {
 
   @OneToOne(() => TransactionCreation, (transactionCreation) => transactionCreation.transaction)
   transactionCreation: TransactionCreation
-
-  static async findByTransactionTypeId(transactionTypeId: number): Promise<Transaction[]> {
-    return this.createQueryBuilder('transaction')
-      .where('transaction.transactionTypeId = :transactionTypeId', {
-        transactionTypeId: transactionTypeId,
-      })
-      .getMany()
-  }
-
-  static async getDecayStartBlock(): Promise<Transaction | undefined> {
-    return this.createQueryBuilder('transaction')
-      .where('transaction.transactionTypeId = :transactionTypeId', { transactionTypeId: 9 })
-      .orderBy('received', 'ASC')
-      .getOne()
-  }
 }
diff --git a/backend/src/typeorm/entity/User.ts b/backend/src/typeorm/entity/User.ts
index 84a40a5cd..ad76bd4a3 100644
--- a/backend/src/typeorm/entity/User.ts
+++ b/backend/src/typeorm/entity/User.ts
@@ -28,25 +28,4 @@ export class User extends BaseEntity {
 
   @Column()
   disabled: boolean
-
-  // Moriz: I am voting for the data mapper implementation.
-  // see: https://typeorm.io/#/active-record-data-mapper/what-is-the-data-mapper-pattern
-  // We should discuss this ASAP
-  static findByPubkeyHex(pubkeyHex: string): Promise<User> {
-    return this.createQueryBuilder('user')
-      .where('hex(user.pubkey) = :pubkeyHex', { pubkeyHex })
-      .getOneOrFail()
-  }
-
-  static async getUsersIndiced(userIds: number[]): Promise<User[]> {
-    const users = await this.createQueryBuilder('user')
-      .select(['user.id', 'user.firstName', 'user.lastName', 'user.email'])
-      .where('user.id IN (:...users)', { users: userIds })
-      .getMany()
-    const usersIndiced: User[] = []
-    users.forEach((value) => {
-      usersIndiced[value.id] = value
-    })
-    return usersIndiced
-  }
 }
diff --git a/backend/src/typeorm/entity/UserTransaction.ts b/backend/src/typeorm/entity/UserTransaction.ts
index 2f5bd69fc..7e24b66b0 100644
--- a/backend/src/typeorm/entity/UserTransaction.ts
+++ b/backend/src/typeorm/entity/UserTransaction.ts
@@ -19,18 +19,4 @@ export class UserTransaction extends BaseEntity {
 
   @Column({ name: 'balance_date', type: 'timestamp' })
   balanceDate: Date
-
-  static findByUserPaged(
-    userId: number,
-    limit: number,
-    offset: number,
-    order: 'ASC' | 'DESC',
-  ): Promise<[UserTransaction[], number]> {
-    return this.createQueryBuilder('userTransaction')
-      .where('userTransaction.userId = :userId', { userId })
-      .orderBy('userTransaction.balanceDate', order)
-      .limit(limit)
-      .offset(offset)
-      .getManyAndCount()
-  }
 }
diff --git a/backend/src/typeorm/repository/Balance.ts b/backend/src/typeorm/repository/Balance.ts
new file mode 100644
index 000000000..2cec58fdf
--- /dev/null
+++ b/backend/src/typeorm/repository/Balance.ts
@@ -0,0 +1,11 @@
+import { EntityRepository, Repository } from 'typeorm'
+import { Balance } from '../entity/Balance'
+
+@EntityRepository(Balance)
+export class BalanceRepository extends Repository<Balance> {
+  findByUser(userId: number): Promise<Balance | undefined> {
+    return this.createQueryBuilder('balance')
+      .where('balance.userId = :userId', { userId })
+      .getOneOrFail()
+  }
+}
diff --git a/backend/src/typeorm/repository/Transaction.ts b/backend/src/typeorm/repository/Transaction.ts
new file mode 100644
index 000000000..2c26fe7b5
--- /dev/null
+++ b/backend/src/typeorm/repository/Transaction.ts
@@ -0,0 +1,28 @@
+import { EntityRepository, Repository } from 'typeorm'
+import { Transaction } from '../entity/Transaction'
+
+@EntityRepository(Transaction)
+export class TransactionRepository extends Repository<Transaction> {
+  async findDecayStartBlock(): Promise<Transaction | undefined> {
+    return this.createQueryBuilder('transaction')
+      .where('transaction.transactionTypeId = :transactionTypeId', { transactionTypeId: 9 })
+      .orderBy('received', 'ASC')
+      .getOne()
+  }
+
+  async joinFullTransactionsByIds(transactionIds: number[]): Promise<Transaction[]> {
+    return this.createQueryBuilder('transaction')
+      .where('transaction.id IN (:...transactions)', { transactions: transactionIds })
+      .leftJoinAndSelect(
+        'transaction.transactionSendCoin',
+        'transactionSendCoin',
+        // 'transactionSendCoin.transaction_id = transaction.id',
+      )
+      .leftJoinAndSelect(
+        'transaction.transactionCreation',
+        'transactionCreation',
+        // 'transactionSendCoin.transaction_id = transaction.id',
+      )
+      .getMany()
+  }
+}
diff --git a/backend/src/typeorm/repository/User.ts b/backend/src/typeorm/repository/User.ts
new file mode 100644
index 000000000..2a2299a4c
--- /dev/null
+++ b/backend/src/typeorm/repository/User.ts
@@ -0,0 +1,23 @@
+import { EntityRepository, Repository } from 'typeorm'
+import { User } from '../entity/User'
+
+@EntityRepository(User)
+export class UserRepository extends Repository<User> {
+  async findByPubkeyHex(pubkeyHex: string): Promise<User> {
+    return this.createQueryBuilder('user')
+      .where('hex(user.pubkey) = :pubkeyHex', { pubkeyHex })
+      .getOneOrFail()
+  }
+
+  async getUsersIndiced(userIds: number[]): Promise<User[]> {
+    const users = await this.createQueryBuilder('user')
+      .select(['user.id', 'user.firstName', 'user.lastName', 'user.email'])
+      .where('user.id IN (:...users)', { users: userIds })
+      .getMany()
+    const usersIndiced: User[] = []
+    users.forEach((value) => {
+      usersIndiced[value.id] = value
+    })
+    return usersIndiced
+  }
+}
diff --git a/backend/src/typeorm/repository/UserTransaction.ts b/backend/src/typeorm/repository/UserTransaction.ts
new file mode 100644
index 000000000..7efd8f12b
--- /dev/null
+++ b/backend/src/typeorm/repository/UserTransaction.ts
@@ -0,0 +1,19 @@
+import { EntityRepository, Repository } from 'typeorm'
+import { UserTransaction } from '../entity/UserTransaction'
+
+@EntityRepository(UserTransaction)
+export class UserTransactionRepository extends Repository<UserTransaction> {
+  findByUserPaged(
+    userId: number,
+    limit: number,
+    offset: number,
+    order: 'ASC' | 'DESC',
+  ): Promise<[UserTransaction[], number]> {
+    return this.createQueryBuilder('userTransaction')
+      .where('userTransaction.userId = :userId', { userId })
+      .orderBy('userTransaction.balanceDate', order)
+      .limit(limit)
+      .offset(offset)
+      .getManyAndCount()
+  }
+}
diff --git a/backend/src/util/decay.ts b/backend/src/util/decay.ts
index 3d39b198f..7b064b0b1 100644
--- a/backend/src/util/decay.ts
+++ b/backend/src/util/decay.ts
@@ -1,4 +1,6 @@
+import { getCustomRepository } from 'typeorm'
 import { Decay } from '../graphql/models/Decay'
+import { TransactionRepository } from '../typeorm/repository/Transaction'
 
 function decayFormula(amount: number, durationInSeconds: number): number {
   return amount * Math.pow(0.99999997802044727, durationInSeconds)
@@ -6,7 +8,8 @@ function decayFormula(amount: number, durationInSeconds: number): number {
 
 async function calculateDecay(amount: number, from: Date, to: Date): Promise<number> {
   // load decay start block
-  const decayStartBlock = await Decay.getDecayStartBlock()
+  const transactionRepository = getCustomRepository(TransactionRepository)
+  const decayStartBlock = await transactionRepository.findDecayStartBlock()
 
   // if decay hasn't started yet we return input amount
   if (!decayStartBlock) return amount
@@ -20,7 +23,8 @@ async function calculateDecayWithInterval(
   from: number | Date,
   to: number | Date,
 ): Promise<Decay> {
-  const decayStartBlock = await Decay.getDecayStartBlock()
+  const transactionRepository = getCustomRepository(TransactionRepository)
+  const decayStartBlock = await transactionRepository.findDecayStartBlock()
 
   const result = new Decay(undefined)
   result.balance = amount