Best raised bed material for Indian terraces?

Fabric raised beds (HDPE) are best for Indian terraces — lightweight, breathable, affordable (₹500–2000 for a 4x2 ft bed), and free-draining. Untreated wood beds rot in India's monsoon humidity within 2–3 years. Galvanised metal is durable but heavy. Avoid railway sleepers (treated with creosote).