What is AAIUViewService on an iPhone?

It is part of iOS, and its particular function is AFAIK undocumented.

If legally and contractually permissible in your area, disassemble the app and look for clues.

It might be inferred that whatever is happening here might be or is separate from telemetry and analytics data, so some background on your particular situation beyond this app might be helpful, as well as how long ago the particular situation started.

A normal user like me do not want to know what these analytics/diagnostic data mean. These should never bother anyone especially when there is no issue with your device.

These are meant for diagnosis when the iPhone goes for service or repair to the Apple Authorised Service center.

If you are experincing some serious issue in the function of the iPhone then...

Take your device to an Apple Retail Store or Apple Authorized Service Provider, or contact Apple Support:

Apple Repair and Repair Status Check - Official Apple Support

Apple Authorized Service Provider

Find Locations - Location Selector - Apple

Contact Apple for support and service - Apple Support 

Alternatively you may ...

Get a Genius Bar Reservation and Apple Support Options - Apple

Contact Genius Bar.

Manage Reservations - My Reservations - Apple

While iPhones don't have a built-in test specifically for performance, there are steps you can take to identify and potentially resolve the issue. Here are a few suggestions:

General troubleshooting:

1. Restart your iPhone: Often, a simple restart can clear temporary glitches and improve performance.
2. Sometimes, a simple restart can resolve temporary software glitches. Turn off your iPhone, wait for a few seconds, and then turn it back on.
   1. 1. Restart the device. That's it.
3. Still not solved --> Force restart iPhone - Apple Support
4. Make sure you have the latest updates installed.
   1. Update Over-the-Air (OTA) —> Update your iPhone or iPad - Apple Support (IN)
   2. Update using iTunes/Finder —> Update your iPhone, iPad, or iPod touch - Apple Support (IN)
5. Force close unused apps: Closing unnecessary apps running in the background can free up memory and improve performance. Double-press the home button (or swipe up from the bottom on newer models) to see all your open apps, swipe up on the app you wish to close. Close an app on your iPhone or iPod touch - Apple Support (IN)
6. Monitor your storage: Low storage space can slow down your iPhone. Go to Settings > General > iPhone Storage to see how much storage space you're using. If you're running low, consider deleting unnecessary files, apps, or photos. Manage and Clear Storage on your iPhone a… - Apple Community

Troubleshooting specific issues:

• Slow internet: Try restarting your Wi-Fi router or resetting your network settings on your iPhone (Settings > General > Reset > Reset Network Settings). Internet not available WiFi and Cellular … - Apple Community
• App performance issues: This could be due to the app itself. Try updating the app or reinstalling it. You can also search online for known issues with the app and potential solutions. Reset Settings - All, Network, Data Plans… - Apple Community
• Battery drain: Check your battery usage in Settings > Battery. This can help you identify apps that are draining your battery and take appropriate action. Prolong and Maximise Battery Performance … - Apple Community

If none of these tips work:

1. Self Service Repair is intended for individuals with the knowledge and experience to repair electronic devices. If you are experienced with the complexities of repairing electronic devices, Self Service Repair provides you with access to genuine Apple parts, tools, and repair manuals to perform your own out-of-warranty repair. Purchase genuine Apple parts and rent or buy professional-grade tools from the Self-Service Repair Store. The online store is operated by a third-party provider ... Self-Service Repair
2. Get a Genius Bar Reservation and Apple Support Options - Apple
   1. When you encounter issues with your Apple devices, the Genius Bar at Apple Retail Stores is the go-to place for expert assistance. The Genius Bar is staffed by knowledgeable Apple employees, often referred to as "Geniuses," who can diagnose and resolve a wide range of hardware and software-related problems. To ensure personalized attention and a convenient visit, Apple provides the option to schedule a Genius Bar Reservation.
   2. Contact Genius Bar. Manage Reservations - My Reservations - Apple
3. Take your device to an Apple Retail Store or Apple Authorized Service Provider, or contact Apple Support:
   1. If you prefer face-to-face assistance, you can visit an Apple Retail Store. Apple Retail Stores are designed to provide a hands-on experience with Apple products and offer support services. You can speak with Apple specialists, known as "Creative Pros" in some locations, who can assist you with product-related inquiries or minor troubleshooting.
   2. In addition to Apple Retail Stores, there are Apple Authorized Service Providers (AASPs) that are authorized to perform repairs on Apple products. AASPs are independent businesses certified by Apple to offer service and repairs for various Apple devices.
   3. If visiting a physical location is not possible or convenient, you can seek support by contacting Apple Support. Apple offers various channels for support, including phone support, live chat, and email. The official Apple Support website provides information on how to reach out to Apple for assistance.
   4. Finally, you can also start a repair log or track the status of existing repairs --> Apple Repair and Repair Status Check - Official Apple Support
4. Contact Apple Support: it is recommended to reach out to Apple Support or visit an authorized service center for further assistance.
5. Visit an Apple store: They can run diagnostics on your phone and potentially offer additional hardware troubleshooting if necessary.

It's important to note that while these steps can help troubleshoot most performance issues, sometimes hardware problems might require professional repair. There are Apple Authorized Service Providers (AASPs) that are authorized to perform repairs on Apple products. AASPs are independent businesses certified by Apple to offer service and repairs for various Apple devices.