SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a848e425c361784e5e2e3561385d0de1c5d36bb7dcea084aedc2a177e7796a5a' 
  AND token = 'OYuekPPdmcWJTVJhDdBwlGFjCbHsJAvfk+UBMSvclpk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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