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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '83f7e2e3cf0a9cadfa0444913f60e8433f0df43dbc8344720971bdbd237b1f5d' 
  AND token = 'nMK1NX0NonLUGNCFIjbTZqfGp5aoqQ5IiyrjJAQB7k0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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