SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f726e8dffa55e138541727e3412d6994eed2fd1b5f1352db82b618eec5282a4a' 
  AND token = 'FHRN+kuY1uvDFPF35bhAv7kMgMFVnOV3gVrf2klaNi8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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