SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad6bd0bf503bf44d9281ad874a05756026ff5ad10e75eae6f03cd30907406821' 
  AND token = 'fnZZ/q+XK7ArKTlbXb9w0jju5r/CKFL5+geRAduzzYw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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