SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7b7397881fe194a54848bb56d1976813bc4e06da90243100f9ce3fb5512df845' 
  AND token = 'BxM4aAndcCiXCjasDYQ7kiMeCAVDr8dqAN+m20CASiw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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