SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a3a1150ebe5b548e827bbabcc8bd52dd42c3b267f4c10251aa0e03bad0c0f62' 
  AND token = 'U6/erkU9x095MJG5VMPzqgwfjt0SlMxsD7Rl7Zv5uFs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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