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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4209a942c941171dd0036f38cf625980e952ab797396e3d4649281bf255503fa' 
  AND token = '1miR5ngVIY0eeBb6IbEdzjkHFoMVxCSa5WmYIfxM/zM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00013

JSON explain

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