SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a831c623465ebe1817757badf2a3df60315436e75cbc1d7fece13d4710e0e6c8' 
  AND token = 'uf6vTHzCGvqvY6s/Q9yzn0jGZJLG6DsQHC3vFp8wfVw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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