SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8147650b903dce85c72682e9618849a740fa7658507d3b045cd1232b228d903c' 
  AND token = 'v51Xsz+XV+SMQN9GXXRyXKqxDFdidGO6SDqoPYShhmg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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