SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '0347db1af5be655cef5874b5eea57cf99706c58c1de4a01f8df6b06303e74892' 
  AND token = '+C850izkAAYirOjymgPx4mLPUVqtA9RMVc443817wtY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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