SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '97ac4677d134333e05e1c706d237eec309d63b378b1403fb49a74f04f42c3dd2' 
  AND token = 'iT8znYpShTmXpVjR77nG4VZgE3TimJrvipdTHFRVxbk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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