SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a88fb6ba3ef5c081a6f4d01fd246bf33d383201d0e91071acb4a24d99f3b1e68' 
  AND token = 'NygjQaWq33bZg9woWRqSCvQkt8V7jpcE/IBYzhs//G8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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