SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71aed6de029acbb35b366e81b8f173d1520478989f7cc6ac3734f241f7a7ab75' 
  AND token = 'r36ew/sC5oqp45luzEcgT+eT/JSBVYXEKR2CUEVQtrE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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