SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eb387395795aad1a0ffd10b53cd256bb9d94d0f4c929231b6644f80c008e3959' 
  AND token = 'D6oVMtuTzFLlrGBnuvHBhU4EekbhuG8WYJultVH4uZs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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