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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9e577ad17bc3a7c4f5eeaa508badcd539f8e6540acb0ee832649cd2a3960f7c1' 
  AND token = 'fZ8Jv7SxbTRtQMKdv48w0DY7PpBUFff8jkMjUCmdTHI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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