SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '831d1cfb1c1577a5675a4024fec4065f974301963eacdcbbee4d604758c142c9' 
  AND token = 'ZGTuyka1Qtxtj91DukIpQz91fl53dQ3UCqYjheXyw30=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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