ATT Fiber Unstable Ping

How is it you're measuring ping spikes when you're not gaming? 

Wi-Fi can have issues for a lot of reasons.  Nothing beats a solid Ethernet cable to the router, and you do not have that.

@JefferMC 

I don't measure ping spikes when I'm not gaming. I just noticed how when I'm browsing or watching movies/shows I never run into any issue. The internet is never noticeably slow and the streaming services never buffer. I can run an ethernet cable to the router, but it's just inconvenient and may be a tripping hazard since my PC and the router are not in close proximity.

So the better statement is that you do not notice ping spikes while doing anything other than gaming, and most of these other activities are not latency sensitive so you would not expect to notice ping spikes.

I understand why you don't want to run an Ethernet cable, but the fact remains that twitch games are latency sensitive and you'll notice issues over Wi-Fi that you'd never notice otherwise.  (I will say that maybe your latency issues don't have to do with the Wi-Fi, but we have no evidence in that direction at this point).  It could be that some new device is in your home and is causing intermittent interference.  It could be some old device in your home has started generating intermittent interference.  It could be that the radios in either your Gateway or Extenders are getting old and are starting to lose the ability to cleanly communicate with each other.   It could be that someone painted a wall in between the two and the extra 2-4 coats of paint are just enough to cause some issues.  Or you have a neighbor who just tweaked his Wi-Fi Router to boost power over FCC regs.  Or...

Same exact issue as original post. This isn't an isolated incident. I've managed to find others reporting the same thing around the same recent timeframe over the last month or so. Slowly ramping latency starting around 8EST, peaking to unplayable levels around 10EST, and gradually going back to normal around 11EST. The first time I noticed this, I did a speed test. Less than 1 down when I'm paying for 1000 down, slightly higher latency. The second time it happened I did another speed test. This time the speedtest was normal (but I was still having the same latency spikes in games). It's amazing to me that the root cause hasn't really been pinpointed yet. It's obviously happening to multiple people and implies a problem with the service itself, yet you have everyone running around trying to diagnose an isolated problem like a surge protector or something.

@MSmith1212 

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 It's amazing to me that the root cause hasn't really been pinpointed yet. It's obviously happening to multiple people and implies a problem with the service itself

This post was one of 3 top results on Google while trying to research my issue, so I assume others having the same issue now will also find this 2-month old post and take some solace in knowing they aren't alone.

I am using the gateway that was provided to me by AT&T upon move-in. My gaming pc is connected to it directly via ethernet. Not sure about DNS service. I haven't messed with DNS settings at all.

Just to recap, absolutely flawless speeds/connection, until about a month ago. Speed is mostly ok, but latency always starts spiking during prime time hours (roughly 8-10 PM EST).

but latency always starts spiking

Latency, even more that bandwidth, is not a single-ended metric.  You must answer Latency to where?  If the answer is "whatever the game says," then where is the game server, and what is your route to that game server?