SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '504a8f1c8b43917399c71d3d94b84a797e60599957d9d78ecea2ec62ef91ca6a' 
  AND token = '2BgL8jo3Xf8BpTuzcfvhOX0w5ebF+QJNvG1dG8/Ze+A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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