SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '249f708256d21157decd2c0afb34a18e523430a4806456d0dba8b9cef3ebf7f5' 
  AND token = '/oqKJL1XAO+tP+LGJ/7f6F1E0aDOqdwHsTxE7ghqXKI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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