SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4b971e3f1962877d2698df5aec8f5d8408166a1153fd2a461090c993e5dfedd6' 
  AND token = 'ZM6YOI4IzLeKylSos8hctYejRuNyvsl4Cu+xezaSzhY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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