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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9d2afbfc67b8f6b76b6a391343b366171ea38d4ef82d53e026e2c86751d7f7b' 
  AND token = '3eiIUnFwZ7F7gU9vcV3xy7c+46sZ8BrQyS9ERUl9AG0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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