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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '847b93d6744c7b20ac34b8292ccea9e6a2abd69ebc0f973a315f930ff0359735' 
  AND token = 'LAWSa57iUzk59W0YhNOlu6Wb5LpovUJ0I/5IE84usso=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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