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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5108966548b8d28b4fd775fab8dc6d08bc6539711322e8c87146660198972657' 
  AND token = 'ys5QEwaDsovA/KZXUu2VYj0SdfHuvo5MroDEWf4ktRQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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