Initial window jump

Shooting and then jumping through the window on the right (green), saves 2 seconds, compared to running in through sliding doors (red), then turning right. This is a big trade-off, as it assumes you are going to pickup the item here at all and it does alert zombies. Is not viable on exetreme, given the damage you take from the glass. Ideally, you wouldn't need this item anyway, in which case either path is the same, but the doors has none of the drawbacks. I personally don't do it, but I always check what spawned there, and if it's worth while, I use the seconds to get the item. But if you are generally just practicing, then why not.

Possible reset point (keycard vs. keys)

From a distance you can see if the double doors are locked/broken. If they are locked, like in the image, the path requires you to get the keycard first, which is fine, but then you have a really long way around, to get to the generator room in the basement. This path is far more dangerous, and over a minute slower at best, so to me it's an instant reset. Thankfully it's only 20-30 seconds in, and appears to be open ~50% of the time.

Navigation

Like anything else in the game, your exact pathing between points, is based much more on zombie and item spawn locations, than anything else. So you have to adjust the path as you go. If nothing else, you might be tempted to jump over the counter (red), as the zombies are usually in here. But given the stamina usage, it is actually slower, than going around the counter (green). You also want to check for spawned items (yellow), and grab them as you run past. The far left one is the most usual spawn. Ideally you wouldn't need the item, but at near no time cost to pickup, why not.

Finding the keys

The keys can spawn multiple places. If you are really unlucky, they can also spawn in cantina/toilet, which is an immediate reset. You won't know this initially though. If they spawned in the offices, they will be in one of the six rooms, on a red janitor cart - This is the que you are looking for. I like to turn right, and check the room on the left first, immediately upon opening the door you know if this is the right room or not. Like in the second image, there are no cart (red), so you move forward. As you move forward down the hallway, look through the glass on the right, if the cart spawned there, you can see it through the window as shown in the image. If not, you check the last room on the left side. If it is in neither of these, you have to make a decision between resetting, or checking the rooms on the other side, which will cost you about 20 - 30 seconds. If it's not in these, then it spawned in cantina or bathroom, and it's a reset. Assuming you get the keys, you dash back out, dodging or killing the zombies in the hallway, as you make it back to lobby.

Getting to the basement

As you exit the blue hall, stick to the left, and go towards the 'green offices'. In here we obviously have to get to the door on the far end. The fastest path is actually not by jumping, but by just dashing between the cubicles (green). However there are several items that spawn in the cubicles, so if you are running on extreme, you likely wanna keep your eyes open. If on easy, take inventory of what resources you got earlier. If nothing, then you might want to jump across (red) a few. I haven't marked item spawn in the image, as there too many to list. If there's a zombie or two in the green path, I usually opt in for the slower jump path.

Pre-using items

When you need to use any item in the game like keys, keycards, boltcutters etc., there is a small delay before the item checks for collision. That means you can actually avoid bumping into the door here, if you use the keys just about a second before you reach the door. That way the door will spring open and you can keep your momentum. Doing so takes a bit of practice, and you watch my runs, you will see me fumble most times. The cost of failing it, is about as small as the gain.

Activating generator

There's a slight randomness to the map here, you might get a left or right path into the basement, it doesn't matter. Simply move forward, activate the generator, check for item spawn on the counters upon exiting the generator room, when exiting turn left, and exit into the large open room of the map. On the shelves in the last actual room, remember to check for ammo spawns, there's usually 1-3 on easy.

Glass skip

When exiting the server part of the basement, if you are running on easy, shoot the glass and exit directly through the glass (green), taking an immediate left. If you are running on hard, this will deal too much damage, so you have to exit through the actual opening, even if the glass is slightly broken already (red). Calling this a skip is probably pushhing it a bit.

Getting to Yellow Hallway

While this room has many things to offer, it also has countless more zombies than you want, so dashing quietly through this is a fast and straight forward thing to do. Simply exit the basement, and hope no zombie is blocking the door (can happen if you made a lot of noise). Up the stairs, up the next stairs, and across the room into the conference location. As you enter the conference room, there's an item spawn sometimes (yellow), on the table, which is why I usually go right around (green). Also note that there's a potential zombie spawn inside on the left, so don't get hit.

Roof or Keycard

Depending on your draw-distance, the keycard reader might not be visible immediately upon entering. If you are unlucky path-wise, the game will have a broken keycard reader, and you have to take the long route across the roof. I won't cover that here, as it's much slower and usually a reset. However, I will say, if you see the sparks [red], then it's roof. If you don't see the sparks [green], err, move a bit closer at first. I've had plenty of times, where there was no sparks, so I assumed it was the keycard path, only to find the rooms empty, and upon going a bit closer, I saw the sparks. So to avoid this annoyance, I usually take a few steps closer. There are between 2-3 seconds between the spark animation, so don't glance.

Finding the keycard

The Red Keycard, can be tricky. It spawns in the offices, on the desks in fixed locations. If you are on easy, the rooms will likely be filled with other stuff to catch your eyes, so run a few times and see where they are located. I usually check the three rooms on the left, and if it's not here, I angrily check one or two on the other side. If it's not here either, it might be downstairs, at which point you might as well reset.

Entering the first labs

In theory you just need to grab a gas-mask from the rack, and enter the airlock. However if you are low on anything, take a glance on your right, down along the three rows of benches, as items usually spawn in at least two of these. Also take the time in the airlock to reload and organize your things, including putting the gas-mask on.

Finding the keycode

In previous versions, you were looking for a piece of paper. Now you are looking for an e-mail, on a computer, with the monitor still turned on. All the other computers have their screens black. This computer can spawn in many locations, so you usually have to check at least a few; but there is a trick. In the map below, I marked all the monitors with a green star. Note that there are others, but I've never seen it appear on these, and some monitors feels more frequent than others. The pathing I use (green), avoids going into the rooms to check, as the doors and zombies takes too much time to navigate around. You usually end up killing more zombies here than you want anyhow. The trick is, you can see which room it is, by simply peering into the rooms from the outside. This is the red dashed lines on the map. For monitors facing you, you can simply see if they are turned on or not (second image, left). For monitors not facing you, you can look for the white interactable outline, which indicates that it's the right monitor (second image, right). It can be hard to see in the screenshot, but it's there. It's a white toon-shader around the 3D model, visible from all sides. That way you only have to enter a single room. When you find the computer, grab the code from the second e-mail, and immediately dash to the elevator. You will have to memorize the code for 5-10 seconds.

Further into the lab

Past the elevator, which is a good point to reload, you have to activate two locks, before you can go in and get the vaccine. In theory you can go either left or right at the initial junction, however if you make too much noise, you risk the zombies blocking the double doors further in, so if you can dodge the hall-way zombies, do it. Don't forget to check for an item (yellow) on the way in, and if you are extremely low resources, there's another spawn at the T-junction ahead, on a crate. I usually skip this, and by chance end up taking left side first. Though you should pick based on zombie spawns.

Chaos, dodging and pathing

If you didn't make noise, you can open the door easily. You want to reach the door on the other side. You will have enough obstacles down here, that you can dodge most zombies through sheer pathing, but do note, that whatever is chasing you on the way into a room, is likely going to block you on the way out. This applies for both rooms. The green path is the most optimal one, but with zombies and their unpredictability, it can be saves to go through the 'kennels' on the side, and behind the vats. The difference is about 3-4 seconds, and in particularly on extreme, worth the loss. Remember inside the rooms, there are weapons in the lockers, and sometimes on the table. Going to the other side, we pass through the middle, you can pick whatever path you want, it's usually down to zombies. I prefer behind the vats, and over the beds. Without overly explaining it, pass through the center into the otherside, activate the lock and run back.

Getting the vaccine

Wether you are playing on extreme or easy, you are likely to be guns blazing from here on out, so don't worry about noise, but also don't worry about clearing anything you don't have to. Run in and get the vaccine. Peer on the table downstairs for an item spawn, and consider if it's needed or not. It takes about 4 seconds to get it if needed. On your way back out, anything that was chasing you, will be coming. It's fairly easy to run-n-gun, and if it's a riot, just bash it and dodge past. When exiting the lab, just go out, the same way you came in, with a little jump across. Then go to the elevator. Please, in the elevator, be sure you are inside it, before you click the button. Due to griefing, they changed how the elevators work, and now if you are half-way in, you get pushed out, and have to wait nearly a minute for the elevator to return. It's a run-ender mistake. Inside the elevator, prepare for one of the hardest parts, combat-wise.

Dashing out of labs

Just before you reach the sliding door, at the first lab, and trigger (red) the zombie wave spawns, make sure your stamina is not empty. Don't sprint all the way from the elevator. You will need near half stamina to make it past the falling zombies, and sometimes, one will already be up, and you might have to kill it. Getting back out to the air-lock, presents the most challenging part of this run. Depending on how much noise you made throughout, and how many zombies you did not kill, there will be two nasty surprises here. Everything you angered earlier, will be waiting for you on the other side of the airlock, and you will have a horde coming towards you from the back. Keep calm, and enter the exit airlock. Pick a weapon that can shoot through thick glass, and start shooting the zombies. But be fast, you have zombies coming in from behind. If you get too close to the exit door, the airlock opens, and the zombies in front of you stream in. When you cleared enough, open the door and bash whatever is left, just so you can dash away. In the next area, zombies will be crawling in, but these can usually be skipped. Exit the labs entirely, taking a left and going up the stairs to the roof. I have lost many runs in the airlock, by accidentally opening the 2nd doors, or letting the following horde catch me while I tried to clear.

Minor jump skip

The obvious path is through the sliding doors, and around to the last stairs (green). If you are feeling lucky, you can jump through the window glass on the right, and jump up on the stairs. I'm unsure if the stamina cost is actually worth it, but it feels good.

The Roof Showdown

Immediately enter the room on top, go left around, and click the radio. Zombies can spawn in here. There's also sometimes ammo or weapons, and usually always a melee weapon on the right side of the room. Now zombies start spawning, and will move in towards you. I usually go outside and shoot a few of them while waiting for the helicopter. You have maybe 30-40 seconds, before the helicopter will call out again. At this point, you need to be ready at the radio button again, to immediately click it the second time. The reason you might want to go outside and shoot zombies in between, instead of just waiting at the button, is the timing. If you stay inside, the zombies will pile through the door, just about the time you need to click the radio the second time. On extreme, this can be dangerous. On easy, it depends on how well and fast your shooting is. Don't risk it. In multiplayer you see most people camp around the red square, near the helipad. This isn't good when speedrunning, as it can get zombies stuck behind the helipad, and slow moving zombies take long to get there. Instead, go hunting. Go to either of the sides, and shoot up to there's nothing left, then cross to the other side. Depending on how lucky you are, you might get everything in one clear on each side. Please note, the zombies in the air and on the roof, don't count. When you hear your phone beep, that means the helicopter is about to land, so dash to the helipad and stand below it on the left, for instant rescue.