SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '303ae9ccdbd46a02eeb8ab417406467336e0317081c5b6d19654bc507c4f2ed3' 
  AND token = 'srCis1uZxyMQ9ypEmI1cZAyNXXUYi/b9pcip9WiYWjM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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