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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8d5fb5df06076ebd7e04041f31e3dd3c6dccb6673e3dc2c646f8e87a5a5648b' 
  AND token = '4isIxtob8rklJ6TSZ6ggW1cP0uilynRrcoKpoCzy/wQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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