SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2b2051cdbee8d92349f2a3eff5b7403d2b1eed0fedf1fe4370c86ae523892fd5' 
  AND token = 't5c0eLBqC+NbUE1o2Tp9bYRzpbZggwunaG6Dr1Vh4Xo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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