SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b3d1d98568b289e45c90d06138200a0ec8eaad73588814774fca24fd7719b1c' 
  AND token = '727QfBqjVCkQC4ljRKqklq8oCzQwdhDBQ0PwNTdDuZg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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