SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81e721ee889974e52543e0a0d6a3175a72cf342a5a6a72e1a548a3ee510c0f35' 
  AND token = '3CFmeOcqrSl2DrwmB7kdhVjfe7qMqeeevjhfGhN3zcU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}