Sandbox

SELECT 
  1 
FROM 
  cscart_ec_print_temp_designs 
WHERE 
  session_id = 'L3HL-8WIJ-8QCC-4UUN-B6ZQ-TS9R-99LR-4YL9' 
  AND product_id = 126 
  AND expires_at > 1770196321 
  AND confirmed = 'Y' 
LIMIT 
  1

Query time 0.00036

JSON explain

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