SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff50b49ac312b84a5facccef9caf2786e17dd173c01d1d56241e8552093ace91' 
  AND token = 'fiLDkBvOWcedtIyBfprs/gxvKp4FCKAKmnVmTrcBnjk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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