SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8b7ec301a800c6c1431249f0a8d284a1a0a0fb5cac694e8c32c107e56266a30' 
  AND token = '0AVnrSWb2PacSgsxxrDBuVfc53N19HjO8/HzjWPJTl8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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