SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eb39c7226004126d7ab9cbf89efaafaae233536de164ac5b2ed16fd13844dc2f' 
  AND token = '5A1vontAYFXizm0IgKengESpdRad8az4TPohybnAPqE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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