SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6b11d09c041ea756c242256bf0b62c6569739fae4add8cb7c9da4367eb57f00' 
  AND token = '3nGXk6SYtD+qQ3DCBVhLGXeB63aTpi7Fs1kwjVi0h4E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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