SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8f82a2a3038b4448454885a0c7c2ae571f08d9e56926861216da74527eea307' 
  AND token = 'L8peeZ8RlXDfuMeXBgJ+liuFHvzWRCkdOB5qOmquOIk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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