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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50eeb3619d8e2a74b73599e8aeb7b51adbfe99f3d50e1a7d04755d09502728f5' 
  AND token = 'hPK+wyUhBpM7hfTJ5zZ7HKcTX1P2axRxDyxxBX/Cmh0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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