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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c5f7c16bf1d324867427f7c8349354ac269e270693942d4c2321dc77bfb523db' 
  AND token = 'SYgHxP5oPhMleIw2SlxVFaaKCXrBKREsJTDrX7KOLyM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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