SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fcd7e8cfa544a315dbe6c52a2f26356d3f999e372221e7b4c742a42720ed693' 
  AND token = 'vNPsrajl4PjhbdHdX38mTzIrpEI3N42e3klokAcGDvM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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