SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8204c706e7259d7455b64a554918c9d91f6d044817a781a37da4f0eed196998e' 
  AND token = '8aRwq34DFfV0gECeo+o4X041cOiajd2UV4ahpNJeEXU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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