SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c33f1be5c89f9b011ee2018b2d1665a8ba711347b7aee5c278ffb042503c7554' 
  AND token = 'KTT4iXmuxCqTil4F3eb2fW86UUmuanlsirvVScr6MR4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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