SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b50a039f56b69a713697690a03258168c635d7d4b2a695ef9eabe7a43ee50f83' 
  AND token = 'beTKhnlrqeLOAJZLSn22xgGovwAfyu6FS+r+YUl3I7M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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