SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '249c9f1fbc7434d21559688f4d08cc2e58863ffd1094526caccdca1f68bc68a9' 
  AND token = 'gkvnlgXEpaXTHM/DQoIkQU1UHjQPWl1iFuhIat58dCg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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