SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3eae4ce88259b14dcc7934733575989745b3bbed9c9e1373bdd25975e5cf7d7' 
  AND token = 'iMp9t2RB4YY/uJ8ymxGJ64qXFPCL+pMKWFjSjRhtBjg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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