SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8b4035ab87c6de75635462ce0ebfb46ecf485e9811dc66023729b3bd8b7beff' 
  AND token = 'hyoAGpDXqLSplk1aQysG+OCaJsobrMDtjcfiCITvjoI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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