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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21b50d8a8b29f5f481e3ca0a8168287e6b3a4795ce5e4bc19b8b982ef2828b2b' 
  AND token = 'zNgWzKVxNSZJld/8KAuE/FuySy3T0PDr516mMDJ8jHs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}