SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '521509aa61d52bf08c1566b2ce7e50a4beaa22b17b845a5f51667445964193ee' 
  AND token = 'EHGGx76+AEGtiJiRECZYhnz8J2NIYak8W5dRl+h69VY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}