SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '581a4b8f23b1dd91023c50cfef66979602ea614b5dee102273c2c03fc82b2419' 
  AND token = '38pkUFrdhklK609R9oTZo//dLViLUypc8QDIzQetI9Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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