SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91b035bade1981683e08bf9404fb3e7ae19a8713049ae2388fe1fbb30c74ac42' 
  AND token = '5G7tfTSEWhUVNQQJfOoQhErdxaXCZDw0HDXbDzX3seg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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