Sandbox

SELECT 
  1 
FROM 
  cscart_aprilec_print_temp_designs 
WHERE 
  session_id = 'S4EA-E5ER-WPEC-HLY5-R06J-L2SB-BV3D-ZWMY' 
  AND product_id = 15 
  AND expires_at > 1777133772 
  AND confirmed = 'Y' 
LIMIT 
  1

Query time 0.00031

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}