SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3502174dd6cf5e0a826e237446c9e811a954624777f0937bfc56ef74e4b5b8fb' 
  AND token = 'D7SYiWPKecJYiUAGP2U25wf/gTXct16PjBvS+JdDe6M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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