SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '20d84838440825efaee4be2ae5d74e7df02c7b5f6798bbceff784b1651bb1d5c' 
  AND token = 'cuokZxM8bTmxJ+zAvZWcWUcGQNFt09PPUYgpD4hq35o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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