Picking & Packing

Mission Pick Fill Strategies Explained

How inventory is allocated to pick tasks — covering sort order, fill patterns, configuration, and common troubleshooting scenarios.

Overview

When a pick task is created, the system must decide which warehouse locations to pull inventory from and how much to take from each. This decision has two independent dimensions:

  • Sort Strategy (set on the product variant) — controls the order locations are considered: PICK, FIFO, or FEFO.

  • Fill Strategy (set via Order Automations or manual allocation) — controls the consumption pattern: PICK_CLEAN or FEWEST_PICKS.

The default fill strategy is PICK_CLEAN when none is specified.

Every pick task follows this sequence: the task is created, locations are sorted by sort strategy, the fill strategy is applied, and then the system fills sequentially until the quantity is met.

Sort Strategies

Before either fill strategy runs, locations are sorted based on the product variant's inventory allocation strategy. This determines the base ordering that fill strategies work from.

PICK

Sorts by warehouse location priority, highest first. Tiebreaker is sequence (lowest first), then name (alphabetical).

FIFO

Sorts by inventory location created date, oldest first. Falls back to PICK priority ordering as a tiebreaker.

FEFO

Sorts by expiration date, earliest first, with null expiration dates sorted last. Falls back to PICK priority ordering as a tiebreaker.

Sort strategy determines the base order. The fill strategy then modifies that order to optimize for a different goal — clean locations or fewer picks.

The “PICK_CLEAN” Strategy

Goal: Empty locations as you go to reduce stranded inventory remnants.

UI label: "Pick Locations Clean" — Fill from each location in order, emptying locations as you go.

How It Works

  1. Locations are first sorted by the product variant's sort strategy (PICK, FIFO, or FEFO).

  2. Locations are grouped based on the sort strategy's primary key.

  3. Within each group, locations are re-sorted so smaller available quantities come first.

  4. The system fills sequentially, draining the smallest locations first within each group before moving to the next.

Grouping Logic

The grouping determines which locations are considered equivalent for the purpose of clean-up sorting.

  • PICK strategy: Locations with the same warehouse location priority are grouped together.

  • FIFO strategy: Locations created on the same calendar day (UTC) are grouped. Items received on the same day are treated as equivalent in age, so remnants can be cleaned up first.

  • FEFO strategy: Locations with the same expiration date (UTC day) are grouped. Locations with no expiration are grouped together as a "no-expiry" group.

Within each group, locations are sorted by available quantity ascending — smallest quantities first — with the original sort order as a tiebreaker when quantities are equal. Between different groups, the original sort strategy order is always preserved.

Example

A task needs 50 units of a PICK-strategy product. Three locations share priority 10:

  • Bin A-1 — 12 units available → picked 1st (smallest in group), fully emptied

  • Bin A-3 — 18 units available → picked 2nd, fully emptied

  • Bin A-2 — 30 units available → picked 3rd, 20 units taken, 10 remain

All three bins share priority 10, placing them in the same group. Sorted smallest-first: 12 → 18 → 30. Result: pick 12 from A-1 (emptied), 18 from A-3 (emptied), 20 from A-2. Two of three locations fully cleared.

Without PICK_CLEAN, the default sort order by sequence/name would spread picks across locations leaving remnants everywhere.

The “FEWEST_PICKS” Strategy

Goal: Minimize the total number of pick tasks by preferring locations with the most inventory.

UI label: "Fewest Picks" — Minimize the number of pick tasks by preferring fuller locations.

How It Works

  1. Locations are first sorted by the product variant's sort strategy (PICK, FIFO, or FEFO).

  2. All locations are then re-sorted by available quantity descending — largest quantities first.

  3. The original sort order is used as a tiebreaker when quantities are equal.

  4. The system fills sequentially from the largest locations until the quantity is met.

Unlike PICK_CLEAN, grouping is ignored — all locations are ranked globally by quantity, overriding the sort strategy's group structure entirely.

Example

A task needs 500 units. Three locations are available:

  • Shelf B — 600 units available → picked 1st, 500 units taken

  • Shelf A — 300 units available → skipped

  • Shelf C — 200 units available → skipped

Shelf B has 600 units — enough to cover the full 500-unit need in a single location visit. Result: 1 pick instead of 2 or more.

Strategy Comparison

“PICK_CLEAN”

  • Optimizes for: Location cleanliness

  • Best when: The warehouse has many partially-filled locations

  • Drawback: May create more individual pick tasks

  • Respects sort groups: Yes — only re-sorts within groups

  • Default: Yes, when no automation is configured

“FEWEST_PICKS”

  • Optimizes for: Fewer pick operations

  • Best when: High-volume orders from well-stocked locations

  • Drawback: May leave many partially-filled locations

  • Respects sort groups: No — re-sorts all locations globally by quantity

  • Default: No — must be explicitly set via Order Automations or manual allocation

How Fill Strategy Is Set

Order Automations (recommended)

Fill strategy is set through Order Automations at Dashboard → Organization → Order Automations. Create a rule with the "Set pick fill strategy" action to automatically assign a fill strategy based on order conditions. This is the preferred method for consistent, rule-based configuration.

Manual Allocation

When manually allocating or reallocating a task from the order detail page, the allocation modal provides a radio group to select between PICK_CLEAN and FEWEST_PICKS. A live preview shows the resulting pick assignments before confirming.

To change fill strategy after allocation, use the Reallocate button on the task in the order detail page. The system reconciles existing pick tasks in place — no delete and recreate required.

Common Support Scenarios

"Why are there so many pick tasks for this order?"

The order is likely using PICK_CLEAN (the default). This strategy prioritizes emptying locations, which can result in more individual picks when inventory is spread across many partially-filled bins. If the customer wants fewer picks, switch to FEWEST_PICKS via Order Automations or use the Reallocate button on the order detail page.

"Why isn't inventory being picked in FIFO/FEFO order?"

Check which fill strategy is active. With PICK_CLEAN, items within the same day (FIFO) or the same expiration date (FEFO) may be picked out of strict timestamp order — this is intentional. Same-day items are treated as equivalent in age, so remnants are cleaned up first within the group. With FEWEST_PICKS, sort strategy ordering is overridden entirely in favor of quantity.

"Can we change the fill strategy after allocation?"

Yes. Use the Reallocate button on the task in the order detail page. This opens the allocation modal where a different strategy can be selected. The system reconciles existing pick tasks in place rather than deleting and recreating them.

"What's the default if no automation is set?"

PICK_CLEAN is the default fill strategy when not explicitly configured. If you're seeing unexpected behavior on an order with no automation rules, assume PICK_CLEAN is in effect.