SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '215b1575e7e71cb199753e4b8b59e213265fdc53f4e3425b009bfb24f8970f0f' 
  AND token = '6KzpuVodjQDiz+Sdrw6EbMjAEnMHVd2KYqyseQF+TxI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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