Problem updating a resource array due to node single thread concurrency - node.js

Question

Tables:
users
user_category
categories
user_id (PK)
user_id (PK)
category_id (PK)
name
category_id (PK)
name
I'm having problems with concurrency on node, I'll describe an example to reproduce the error I have:
When receiving 5 requests in parallel to perform a PUT on the same existing user and their categories:
PUT users/userId123
body
{
"name": "other name"
"categories" : [
"categoryId123",
"categoryId456",
"categoryId789",
]
}
Upon receiving this payload in a simulation, first a DELETE query is performed on user_category and then an INSERT on user_category to insert the new categories.
It turns out that as the node is a single thread, the main thread competes, and when performing 5 identical requests in parallel, it is happening to perform two DELETES of two different requests and then the 2 INSERTs, which will generate a primary key error in the table user_category, I already tried to use a transaction for these two queries, but the error still occurs, blocking the main thread until doing these two operations is not an option defied the loss in performance.
Attempt-1
Below is an excerpt from UserController code that does this
if (Array.isArray(user.categories)) {
await userCategoriesRepository.deleteHardByUserId(user.userId)
const userCategories = []
for (const categoryId of user.categories) {
userCategories.push({userId: user.userId, categoryId})
}
await userCategoriesRepository.save(userCategories)
}
UserRepository:
save (userCategories: ICreateUserCategoryDTO[]): Promise<void> {
try {
return this.repository.insert(userCategories)
} catch (error) {
throw new Error(error)
}
}
deleteHardByUserId (userId: string): Promise<void> {
try {
return this.repository.delete({ userId })
} catch (error) {
throw new Error(error)
}
}
Attempt-2 (Transaction)
Below is an excerpt from UserController code that does this
if (Array.isArray(user.categories)) {
const userCategories = []
for (const categoryId of user.categories) {
userCategories.push({userId: user.userId, categoryId})
}
await userCategoriesRepository.updateWithTransaction(userId, userCategories)
}
UserRepository:
async updateWithTransaction (userId: string, userCategories: ICreateUserCategoryDTO[]) {
try {
return getManager().transaction(async transaction => {
await transaction.delete(UserCategory, { userId })
await transaction.insert(UserCategory, userCategories)
})
} catch (error) {
throw new Error(error)
}
}
QUERY LOGGING
case: 1 request (SUCESS)
query: START TRANSACTION // REQUEST 1
query: DELETE FROM "user_category" WHERE "user_id" = $1 -- PARAMETERS: ["userId123"] // REQUEST 1
query: INSERT INTO "user_category"("user_id", "category_id") VALUES ($1, $2) -- PARAMETERS: ["userId123", "categoryId123"] // REQUEST 1
query: COMMIT // REQUEST 1
case: 2 or more requests parallel (ERROR PK)
query: START TRANSACTION // REQUEST 1
query: DELETE FROM "user_category" WHERE "user_id" = $1 -- PARAMETERS: ["userId123"] // REQUEST 1
query: START TRANSACTION // REQUEST 2
query: DELETE FROM "user_category" WHERE "user_id" = $1 -- PARAMETERS: ["userId123"] // REQUEST 2
query: INSERT INTO "user_category"("user_id", "category_id") VALUES ($1, $2) -- PARAMETERS: ["userId123", "categoryId123"] // REQUEST 1
query: COMMIT // REQUEST 1
query: INSERT INTO "user_category"("user_id", "category_id") VALUES ($1, $2), ($3, $4) -- PARAMETERS: ["userId123", "categoryId123", "userId123", "categoryId456"] // REQUEST 2 --> PK ERROR
query: COMMIT // REQUEST 2
Details:
node 16.13.1
typeorm 4.3.2
pg 8.4.0
npm 8.3.0
Postgres database 13.2