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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21c6a3de60ee6660c750a04d581e1dd92a2b92cee4a91aa8476e46cd82f53898' 
  AND token = 'vNzVe9Kx0JoD+srCKRjvDlAB7Hu/HsgshAcCC9TChiQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}