SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76ffd4a751c190bd55ba56d0744a41212099d8fdbca93bf85501593979300fe3' 
  AND token = 'WDriO7QtObc74Nf4fi+2vBcF06STY6TdcBO4ZQgEhNM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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