SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52e7988b4663a1847169256e32de9e769408af41cd75e88f20abfbbdca2485b8' 
  AND token = 'btlmqK9Cy1qW0oJpHoVJzhgsDG8c1gXppQwv4CqUWME=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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