SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b296e50e01ab6f51a33db61b783fadc5728eac6b00c2315bbc3945ce7f1fe31' 
  AND token = 'fZdij3SDGn/PPp1NYS1dPYhQ46pZMk/Xwn78E6XTJ6Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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