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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7e9e476114431e226b69b22e36c3539bac1d231b9246f988bb15a8feb86d6f8' 
  AND token = 'Nmk0G1WlQhzz7uCfNtwdnRmAR7PeVKM1TskSDVq1/YA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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