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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4f0a10fa3ff6579e29eb4fd8d66e5c0661e81dcfdedff305e983562df88ba668' 
  AND token = 'h2NkrK5DThMmrryXikPU9hXoimAd2oCuCCLTUTNe86I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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