SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78f8c94a1e22d343b12cb39fe6b9aadad8388023ced5844096f863439a92b060' 
  AND token = 'lk46BvkEebTrYjcI9iZKaOHTshfMlgGSCG2ruewFRxA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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