SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe719ea5beb08e67ab57f5bf7a94e7f2abccab483ee1f2daaaeafae9ce636012' 
  AND token = 'SUVFqpTbCPnuZVzCFQUimtohqxjFK2ctR+uBEtdVUrU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}