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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3efd75eb47069c97dbd09176a1d8a38d1b07bc998e5f7934ac8bb0d61927e704' 
  AND token = 'KcSdvf1W1l23AfgN8qfg3guFd+UiGBysMvR46EHyNp0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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