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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6ea1b20ec62786a7711a58fc3481e7829e37695c443791fe8473f0d2d544bbe' 
  AND token = '+waNqMoVH+MdFZTOFr1NjxY6F3ZXrrl1iWTlEA9SMvg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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