SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b39cba03bdfa4b8e09f26ea96c51a1c235b13f260c20e2a5ac303e2fc03ceb13' 
  AND token = 'Gw/1fExuo9jM0yKm4qWh29NP+D2a194kTeZmeiPEeDM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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