SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18e5106f2bde5f683b4b29596d7bb06cbc45302fc45d479a65764ee521b71821' 
  AND token = 'JmKtMctiwTnKY29WXP+hTZpsKO/ymdyInImpsvmuiE8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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