SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8942e275bfe3e15128edb0b55bb4677705a97425637067afb1f9adf68519aa2' 
  AND token = 'YBhHmT+iy/HDJgDpwZYx2NP/TsS3722VWZcnUqyJ13g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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