SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e9d9767583aa437082e47a14c36d9707bc4573440c4184d24ec66b388617a303' 
  AND token = 'T4hK2PMSFWc/+h0T/TFHwZvgKJjdVeZwiKzQfTo1SMM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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