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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83724c5a9f77375270ea2d4976024dfa261a2061129037b4278227914792b2aa' 
  AND token = 'CVz8uMAL9nTx9vaVcUz2P0IQy0y69PYiaeZFGaVThqA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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