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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '137eed351df6b850160f406eac1ad0f728b240578b3595a48a4432679ad2fc36' 
  AND token = 'xr3gZPk209yce3ZE6NzI+0fxG7Eoe6GmvSVMyjWVVfs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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