SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8dd89e2d5f5d3a148fb67e5fe4cbf3858631372cc822d624c52e4c1bec5f71e' 
  AND token = 'kLHTehFOPXK7j3AdaSBspfxWRYkAQkSML8gkqJ6NlNU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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