Very minor, wondering if we should add some hyphens in pushnotificationconfigstore

@fjuma I'm not sure :-) I originally had some, but then noticed that the taskstore one did not. But I agree it is a bit long.
How about push-notification-config-store, and renaming the other one to task-store?

That sounds good to me.

For persisting a new entity instance, em.persist() is generally preferred over em.merge(). While merge works, it's designed to handle detached entities by copying their state to a managed instance. Since you've confirmed the entity is new with em.find(), using persist is more idiomatic and can be slightly more efficient as it doesn't need to perform a check to see if the entity is already managed.

                // Create new entity
                JpaPushNotificationConfig jpaConfig = JpaPushNotificationConfig.createFromConfig(taskId, notificationConfig);
                em.persist(jpaConfig);
                LOGGER.debug("Persisted new PushNotificationConfig for Task '{}' with ID: {}",
                        taskId, notificationConfig.id());
            

The catch (Exception e) block is too broad. It's better to catch more specific exceptions. In this context, the operations within the try block (JPA queries and stream processing of deserialized objects) are expected to throw RuntimeException subclasses (like PersistenceException or the one we throw for JSON errors). Catching Exception could unintentionally catch checked exceptions that are not declared in the method signature, or other unexpected exceptions. To make the code safer and more explicit, you should catch RuntimeException.

        } catch (RuntimeException e) {
            LOGGER.error("Failed to retrieve PushNotificationConfigs for Task '{}'", taskId, e);
            throw e;
        }

The setConfig method's responsibility is a bit unclear because it contains logic to set the entity's ID. An entity's primary key should be immutable after it's been persisted. While the logic is guarded by a null check, it's better to separate the concerns of creation and updating. The createFromConfig factory method already handles ID assignment during creation. This method should focus solely on updating the configuration data of an existing entity.

I suggest simplifying setConfig to only update the configJson and config fields, and removing the taskId parameter. The call in JpaDatabasePushNotificationConfigStore would then be simplified to existingJpaConfig.setConfig(notificationConfig);.

    public void setConfig(PushNotificationConfig config) throws JsonProcessingException {
        configJson = Utils.OBJECT_MAPPER.writeValueAsString(config);
        this.config = config;
    }