SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f4b163d3f49921c2934762057fcff202847ae598395c9ac8282d5cbb7b1e8e50' 
  AND token = 'OiwobZg7kldR4rYiL6lWtxQX7tqqcraJSno2q6celq0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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