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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b8415119a68127e829f3d9bec90d7ae6b3811422d71ef43ff4c7ef2c2507fac8' 
  AND token = 'KdkDwznqOf/N8TflfabLno+CWaWL9luPHB6kXvyhj2E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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