SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51358421b62e881be464ed795ae45c71bd99006600564f675f1fbf26b4388df3' 
  AND token = 'L7n4QBsY4zpC8oMxqKLxSNlROu3UVFUechx/e1KUe1s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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