SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '40b9a7d37c624615a755b227f5de85fc42c36838b4c518be170697657db53f4d' 
  AND token = 'xqgo049Ee/Vb6JCPlQUkdSN9dAuAwdC/KZhELnlXGR8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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