SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '103a038e8fb03edfdd9bfea363e2b81e0015bfd99009987f503d253462dc1582' 
  AND token = 't1ZmXTEpV9DpuJFQs4FQQxU/PT1RrXtKEG07NUp1XS0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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