SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fff0b8e452d602779d655c97bf309a9c89353740400048c5b6fbe3f0bc18ed52' 
  AND token = '1qsNK/DYnuEB0UCDaKVCt6kS0u6RutrKKAnRaPMrJmM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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