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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8efb75c8963b9ae758539f67ea9b2b9d4302be00825f8a7aec0e0a7e7ffac325' 
  AND token = 'rRN9DxJ+j6j6GtDY1fAeHysWYznEL6wYk7jyxG5DZZo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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