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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a21c87f71db6e9390e87aab8d83bb01f164b559a3f545765b3fb9af2f3c211a2' 
  AND token = 'q6duEDp6WKPl/FTaPkOVGHaalA99TVGS2D2JO7asfCE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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