SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'b8ff1f028dccf1447046ef8065c34b5444a053b5e6240ab54349b978be062781' 
  AND token = 'LwDhngm8qZWxNZfDnRxd+AlCGGnZR83g66LtUNjAkWk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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