SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8dff9a6102710eabfa73401e3b37cff75a91674ff9a26f10b1b7117c6119645' 
  AND token = '99JiTT2tib2KSK7lBuKtN4c3QxwWtr5Sz49+e/QzYGc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00053

JSON explain

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