SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a2e737be037967bcfada9b52bb8b4716827e22d15e0744d07a7486ece0a12193' 
  AND token = 'JtA8S8T/E9ZI0+uAP7gtfPEtdEas2C+boe473WvGLjg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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