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Posted on • Originally published at processcamp.io

The Race Track: Parallel Work in BPMN

#bpmn #processmodeling #tutorial #learning

The Token

Before we hit the racetrack, you need to understand one concept that makes BPMN click:
the token.

Imagine a marble rolling through your process diagram. It starts at the start event,
passes through tasks one by one, and eventually reaches the end event. When a task is being
worked on, the marble sits there and waits. When the task is done, the marble rolls
forward to the next element.

At an exclusive gateway (which you learned in the Shoe Shop), the marble takes one path.
Simple. But what happens when work needs to happen at the same time?

  > **Token concept:** Imagine a marble rolling through your diagram. At a parallel
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gateway, the marble is cloned. At an exclusive gateway, the marble picks one path.
At a closing gateway, the marbles merge back into one.

  ## Meet Gonzalez
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Gonzalez is a Formula One driver. Successful, famously impatient, and leading the field
in the final race of the season. Ten laps in, he needs a pit stop. His team has to
** change the tires** and refuel the car - and they need to do
it simultaneously. Every second in the pit costs positions on the track.

If the fuel team had to wait for the wheel team to finish, or vice versa, the pit stop
would take twice as long. Gonzalez would lose the championship. The process needs to
express: "these things happen at the same time."

  ## The Parallel Gateway
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That's what the parallel gateway does. It looks like a diamond with a
** plus sign** inside - and unlike the exclusive gateway, it has no question
on top. No decision is being made. It simply says: "all paths activate simultaneously."

Back to the token concept: when the marble hits a parallel gateway, it gets cloned.
If there are two outgoing paths, you now have two marbles. Three paths, three marbles.
Each one rolls independently through its branch.

At the other end, a closing parallel gateway waits. It knows how many
marbles to expect. It won't release a single marble until all of them have arrived.
That's the synchronization point - the moment where parallel work comes back together.

  > **Parallel gateways** are diamonds with a plus sign. They activate all outgoing
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paths at once - the token is cloned. The closing gateway waits for every clone to arrive
before releasing a single token forward.

  ## The Pit Stop
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Here's how Gonzalez's pit stop works in BPMN:

The process starts when Gonzalez pulls into the pit lane. The token hits the parallel
gateway and splits into two:

  - **Wheel team path:** Loosen screws → Remove tires → Mount new tires → Fasten screws
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  • Fuel team path: Open gas cap → Refuel tank → Close gas cap

Both teams work at the same time. The wheel team is fast - four tasks done in seconds.
The fuel team is slightly slower - refueling takes longer. Gonzalez is getting nervous.

But the closing gateway waits patiently. It doesn't release Gonzalez until both tokens
arrive. The fuel team closes the gas cap, the second token reaches the gateway, and
Gonzalez rockets back onto the track.

  ## Why This Matters
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The parallel gateway isn't just for racing. It shows up everywhere:

  - A hiring process where reference checks and background verification happen simultaneously
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  • An order process where payment processing and warehouse picking happen in parallel
  • A patient admission where insurance verification and room assignment happen at the same time

Whenever you hear "at the same time," "simultaneously," or "in parallel" - that's a
parallel gateway.

  ## Don't Confuse the Gateways
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The exclusive gateway (X) and parallel gateway (+) look similar. Even experienced modelers
mix them up. Build a mental bridge now:

  - **Exclusive (X):** Think "cross out" - you're crossing out all paths except one
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  • Parallel (+): Think "plus" - you're adding all paths together

One makes a choice. The other doesn't choose - it does everything.

  > **Exclusive (X):** Cross out all paths except one.
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** Parallel (+):** Add all paths together. Build this mental bridge now -
it will save you from the traps in Chapter 4.

This is part of the Learn BPMN series on ProcessCamp - 11 real-world scenarios to master process modeling. Try modeling this yourself in Crismo - free, no signup needed.

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