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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '972c37eda67e2516a93e180caf30217e5f551256b4f9a733aebc69ca95ee6faa' 
  AND token = 'fmq0gpGDn1juWzsaoEVNBdKalh4qYj2+DylGuTYARdE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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