SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75276b77677983b22565f83dab435c825207c81433cbe39213e655595cf49ed1' 
  AND token = '6qUh/OXu9tjLnrt6dIzLSTw7OiYHT8qV93xfSN2BuMk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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