SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b9b28169477617ad49222a8eccf1aed6048f4138882cf295b41713e944d4c99' 
  AND token = 'jLJycMO3XW18KC7uI4MeUka036A2sr2EckpbC/966wQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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