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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eeca792a28177c5476010513c7be9eb9394a48575c40e5e242cc54ef99d8c92a' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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