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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8a768b3c423687f90f7e15d55cadfb75757b16ec5ecb69eda8d3add0734658c3' 
  AND token = '9Fr2EdB2ES/fTYlvk5WOEPDDsQAqmZ7RlgiRrcqBzC8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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