SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76b83517e398768364d55863b281ead4cee962acb76097aa8248f77d1dccf5f4' 
  AND token = 'Jv/uA0Siyz8MdzQTdvPl9QWmq2L4m+mOkhc7Tr+Fujg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00062

JSON explain

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