SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56c0ce8d291f5a5206948c25b1655f740f4f82392388c72d6bb98c777a983899' 
  AND token = '4p2VEltq1G4YOdhg8USGLhw/0Iz95VWlXywWzo2mQ50=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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