SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '25c76e49a100579073f16df120de223086efcaafc7e97e6321da5a3fc97b79aa' 
  AND token = '4KZv+kWFDBhXKGiKFuI+X+VA3dXqAhBoxUzZxUrOgTQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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