SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a0803d1fe2f7cdf274632b92a1cd4a617217aa2ad6bdeb83cf5b54b5c9fa6186' 
  AND token = 's5TDp1LgRMF/wr4V49vVbMTJ+rQ5HGRYazxgTB9/6qo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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