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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '912e8230a39807dc89dabc7f124cbd2f0a7c260be3859b8dbbbc3af3e1baab09' 
  AND token = 'ePUaLtqF/ws3JL8cp+nY9xSicqQMIUnvn2qCAfHcg+M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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