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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6fa38341d802f93da01c9e347732f2287d14d5a15765bdca373724aae793ec43' 
  AND token = '4wCwCYnp2dhsMu72ErQ472Rvi2ojsONnAargT7adzrI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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