SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71289a11a115b55469b302f055fb1c1e62c938a1b0108e51c003628facff590d' 
  AND token = 'kE0/Rhmgr2C+MOstiYFPhxgAyGyINS4QWQv5sfU6rME=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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