SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2c9688df88b8f22f8c4908bcdcdf12142165382c54f010be02ae803ef2fba28' 
  AND token = '/zzG8AFDfartDyRDq6NkpQ2bpFaSSnpdHhvOOmU/6WE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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