SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '312aaf4157b5f890494c52336ccf4d171637f8683cba5a7c2aafd2e7989b7839' 
  AND token = 'X5wZiqVpnOHSST0XMud766ajRqdMgQYczexEbDcbWPg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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