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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52fe50c798ca3cd138a098ea6622b953f933c1aeeed79cd7d1ea119a0048fb78' 
  AND token = 'GU81XYGqiHZzIvuZbH5MdiKjHgM/EbyXfyQLt2qDnO0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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