SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68981b782eee5dfef38d9f47bd7e0d4b039e6e0e0cd60428e482b1b26ca7e21e' 
  AND token = 'dE6p/qnTLAnUF6ABDwljiMBwagyGdFk/TikPVSlMv5I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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