While cleaning up unused files doesn't directly have an impact on performance, Android does start to slow down when you run out of internal storage.

Most Fire tablets don't have much internal space, so many device owners choose to put in a microSD card.

Older Fire tablets let you move some apps to the microSD card, but if you have one of the newer models with Android 7.0 Nougat (like the 2019 Fire 7 or 2018 Fire HD 8), you can actually use an SD card as an extension to your internal storage.

However, moving apps to your SD card actually make your Fire tablet slower.

As we've covered in detail, even the fastest microSD cards are slower than the internal storage used by modern phones and tablets.

We tested this 16GB SanDisk A2 microSD card (A2 cards are supposed to be the best for apps) with a 7th-generation Fire HD 8, and random read speeds were 3x slower than the internal storage, with even worse random write speeds.

In other words, even one of the fastest microSD cards is twice as slow as the Fire tablet's internal storage.

Disk benchmarks on internal storage (left) and Class 10 A2 microSD (right).

These are among the lowest-grade SD cards you can still buy, and as you can see in the screenshots below, random read performance was around 6x slower than the internal storage.

Random write speeds were unusable, at 35x slower than internal storage.

Disk benchmarks on internal storage (left) and Class 10 microSD (right).

It's important to note that SD card speeds don't matter if you're only using them for data storage.

If you really need the extra storage for apps, get an A2-rated card like this SanDisk model.

Your apps will still run slower, but they won't be as slow as they could be.

If your Fire tablet is still slow, there's one more option you can try — Android has a hidden setting for limiting the number of applications that can run in the background

Once you get access, open the Settings app, select 'Device Options,' tap 'Developer Options,' press 'Background process limit' (it's near the bottom), and set it to 2 processes

Now your Fire tablet will only keep two apps running in the background, at a maximum