SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f55016e9816809d2d546c12de5850100ea5062feb8c632a434ba7893566ead90' 
  AND token = 'iEqAfGga954bvPsGjdGBDtElGeBAsf+i5zUox7xyRfw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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