SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1cc0d8e26fbb5488dc8a38ea72542af0b142a30ac73c835919fdb01558af8a4e' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00012

JSON explain

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