SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83ad63ecbc3832ec7cedbd1b13807ed49e49ad76ff0809c5791aabaa81a66402' 
  AND token = 'My34taOKSwLaO+mU8wGbtjZR30FvKDy3lEazvkNAuDg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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