SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7669efbb3371ef495cbf6b751d0fc4ba117e76a64c5e9884955bb50ce73ea68' 
  AND token = 'g7GQnlPprvO/homBpV+BmWeG5CFdBUd5plA+prlj3QE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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