SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a9818c931c6902f4fe262623d53be02fcf95372d063f3b62c15ee498109b990f' 
  AND token = 'kAJSeuGE1yoxtVIqSmSG0xE+pk6woXyooOIHgT+EWq0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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