SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8be255d9cfc08cd402439f1f35f147437994e967f8c90e31f947dc283091ee2f' 
  AND token = 'jl4ftYqMPDHuXZ5ZUbLUoyJx2yqF5oLyVYnBdfH25zs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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