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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef9b9f825a89cace162a0aad6f4a2acf37ab942fd529f72df1ce1cf733c35d4a' 
  AND token = 'mnLVbG+gWiOkYr8tJ9hyADXmuchBMQaSRUTbQKk84tQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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