SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b50bbc767f39f245483527aab8f610b126c446e78eae1f7b59ac66c0a21599a' 
  AND token = '/XAyLWiHJ5+tRObZ3b6wQJ/5NSGmBypk0voyKgym+CE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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