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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b992919e3d1927ed3fd4167ff608343f0d9abbecd75eef182fa14b00b60679f' 
  AND token = 'elourMSR3XY1LjAglnVWCl1buufkRMP6CcwNRH6mbfo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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