SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75858a84c38e8459f57c1198f50d2aefb63117e9e8f00f4dc373318909dcfef7' 
  AND token = 'DocJNfWubnC2s5uWmdKo8QF1KQadTStkvihT6OVUHNA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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