SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e21c708e718eb1276129766c029a77006cf63ebfe3b9a05f1c07e62bf429566d' 
  AND token = 'KCVNZW6z+qsJZxZcLf74okGmm+LlJMNPv0qTTDwtXG4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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