SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1861ea4ceefa0983052a4b96672e31073e1645dc3d02140c2607c8857e4243f2' 
  AND token = 'Wiq7dpBSMUoPEZ5jaMBqQSGn0HYiGzXdK/nkl6kXttU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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