Nursing-bra B-K cup matrix, how do you handle the sizing complexity in Magento?

Nursing bras need a B-K (sometimes B-L) cup range, that’s 10-11 cup sizes vs. 4-5 in standard apparel. Combined with band sizes 30-46 (8 bands), that’s up to ~90 size variants per SKU. Then layer access-flap type (drop-cup, clip-down, crossover, sleep-bra pull-aside, 4 variants) and you’re at ~360 variants per SKU. Shopify’s 100-variant ceiling breaks here; Magento handles it as configurable + simple products.

The model:

• Configurable product = the master SKU (e.g. “Bravado Body Silk Seamless Nursing Bra”).
• Three attribute axes: band_size (30-46), cup_size (B, K), access_flap (drop-cup / clip-down / crossover / pull-aside).
• Simple child products per combination, only the SKUs you actually stock (you don’t need every band-cup-flap combination; typically 30-80 active children per master).
• Custom EAV for post-mastectomy line, post_mastectomy_safe boolean attribute, separately filterable on PLP.

The UX layer matters as much as the schema:

• Fit-guide modal on PDP, pre-pregnancy size + current trimester + weight gain → recommended band + cup. I usually base this on the brand’s published fit-guide (Kindred Bravely, Bravado, Cake all publish theirs publicly).
• Size-up reminders through pregnancy + into nursing (cups typically go up 1-2 sizes from pre-pregnancy to engorgement at week 6 postpartum).
• Lazy-loaded swatch images for the access-flap variants (4 thumbnails per PDP), Hyvä-native.

Performance stays predictable at this matrix size because Magento’s EAV indexing handles 360-variant masters cleanly, the catalog-product-flat indexer is what slows at scale, and it’s off in modern Hyvä builds.